Why the fork?

• The original MSDN C# examples use the SQL Query / DSL Linq syntax instead for the more generally accepted Extension method/lambda syntax.
  • which is very similar to Dart
  • has all the methods such as Distinct, Take, Union First etc so that you don't have to mix the styles (see mixed syntax example below)
• This fork uses more up to date C# syntax, including the var keyword wherever possible and string interpolatation
• This fork has included the modified C# source locally so that you don't have to visit the outdated MSDN site.
• This fork has included a Operation Comparison Matrix

Mixed syntax (bad)

var categoryNames = ( 
    from p in products 
    select p.Category) 
    .Distinct(); 

• The SQL / DSL Linq syntax is more long winded.

Lonq winded Linq syntax

var sortedWords =
    from w in words
    orderby w
    select w;

More succinct extension method Linq syntax

var sortedWords = words
    .OrderBy(x => x);

101 LINQ Samples in Dart

Port of the C# 101 LINQ Samples rewritten into idiomatic Dart and utilizing its functional collection mixins.

Compare Dart to other LINQ examples written in:

• Swift
• Java
• Kotlin
• Clojure
• Elixir
• Templates

Contents

The samples below mirrors the C# LINQ samples layout with the names of the top-level Dart methods matching their corresponding C# examples.

Operation Comparison Matrix

Operation	C#	Dart	Comment
Restriction	Where	where
Projection	Select	map
	SelectMany	expand
Partitioning	Take	take
	TakeWhile	takeWhile
	Skip	skip
	SkipWhile	skipWhile
Ordering	OrderBy		Custom order utility added
	OrderByDescending		Custom order utility added, followed by reversed
	ThenBy		Custom order utility added
	ThenByDescending		Custom order utility added, followed by reversed
	Reverse	reverse
Grouping	GroupBy		Custom group utility added
Sets	Distinct	toSet
	Union	union
	Interect	intersection
	Except	difference
Conversion	ToArray	toList
	ToList	toList
	ToDictionary		Custom toMap utility added
	OfType		Custom ofType utility added
Element	First	first
	First(lambda)	firstWhere(lambda)
	FirstOrDefault	firstWhere(lambda, default)
	ElementAt	elementAt
Generation	Enumerable.Range		Custom range utility added
	Enumerable.Repeat	List.filled
Quantifiers	Any	any
	All	every
Aggregate	Count	length
	Count(lamda)	where(lambda).length
	Sum		Custom sum utility added
	Min		Custom min utility added
	Max		Custom max utility added
	Avg		Custom avg utility added
	Sum(lambda)		Custom sum utility added
	Min(lambda)		Custom min utility added
	Max(lambda)		Custom max utility added
	Avg(lambda)		Custom avg utility added
	Aggregate	reduce
	Aggregate(seed)	fold
Miscellaneous	Concat		Custom concat utility added
	SequenceEqual	SequenceEqual
Join	Join		Custom join utility added
	GroupJoin		Custom joinGroup utility added

Source

• Restriction Operators
  • Dart
  • C#
• Projection Operators
  • Dart
  • C#
• Partitioning Operators
  • Dart
  • C#
• Ordering Operators
  • Dart
  • C#
• Grouping Operators
  • Dart
  • C#
• Set Operators
  • Dart
  • C#
• Conversion Operators
  • Dart
  • C#
• Element Operators
  • Dart
  • C#
• Generation Operators
  • Dart
  • C#
• Quantifiers
  • Dart
  • C#
• Aggregate Operators
  • Dart
  • C#
• Miscellaneous Operators
  • Dart
  • C#
• Query Execution
  • Dart
  • C#
• Join Operators
  • Dart
  • C#

Side-by-side - C# LINQ vs Dart functional collections

For a side-by-side comparison, the original C# source code is displayed above the equivalent Dart translation.

• The Output shows the console output of running the Dart sample.
• Outputs ending with ... illustrates only a partial response is displayed.
• The source-code for C# and Dart utils used are included once under the first section they're used in.
• The C# ObjectDumper util used is downloadable from MSDN - ObjectDumper.zip

LINQ - Restriction Operators

linq1: Where - Simple 1

//c#
public void Linq1() 
{ 
    var numbers = new int[] { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

    var lowNums = numbers
        .Where(n => n < 5);

    Console.WriteLine("Numbers < 5:");
    lowNums.ForEach((x) => Console.WriteLine(x));
}  

//dart
linq1(){
  var numbers = [5, 4, 1, 3, 9, 8, 6, 7, 2, 0]; 
  
  var lowNums = numbers
    .where((n) => n < 5); 
  
  print("Numbers < 5:"); 
  lowNums.forEach(print);
}

Output

Numbers < 5:
4
1
3
2
0

linq2: Where - Simple 2

//c#
public void Linq2() 
{ 
    var products = GetProductList();

    var soldOutProducts = products
        .Where(p => p.UnitsInStock == 0);

    Console.WriteLine("Sold out products:");
    soldOutProducts.ForEach(x => Console.WriteLine($"{x.ProductName} is sold out!"));
} 

//dart
linq2(){
  var products = productsList(); 
  
  var soldOutProducts = products
    .where((p) => p.unitsInStock == 0);
  
  print("Sold out products:");
  soldOutProducts.forEach((p) => print("${p.productName} is sold out!"));
}

Output

Sold out products:
Chef Anton's Gumbo Mix is sold out!
Alice Mutton is sold out!
Th�ringer Rostbratwurst is sold out!
Gorgonzola Telino is sold out!
Perth Pasties is sold out!

linq3: Where - Simple 3

//c#
public void Linq3() 
{ 
    var products = GetProductList();

    var expensiveInStockProducts = products
        .Where(p => p.UnitsInStock > 0 && p.UnitPrice > 3.00M);

    Console.WriteLine("In-stock products that cost more than 3.00:");
    expensiveInStockProducts.ForEach((product) => Console.WriteLine($"{product.ProductName} is in stock and costs more than 3.00."));
  
} 

//dart
linq3(){  
  var products = productsList(); 
  
  var expensiveInStockProducts = products
    .where((p) => p.unitsInStock > 0 && p.unitPrice > 3.00);
      
  print("In-stock products that cost more than 3.00:");
  expensiveInStockProducts.forEach((p) =>
    print("${p.productName} is in stock and costs more than 3.00."));
} 

Output

In-stock products that cost more than 3.00:
Chai is in stock and costs more than 3.00.
Chang is in stock and costs more than 3.00.
Aniseed Syrup is in stock and costs more than 3.00.
...

linq4: Where - Drilldown

//c#
public void Linq4() 
{ 
    var customers = GetCustomerList();

    Console.WriteLine("Customers from Washington and their orders:");
    var waCustomers = customers
        .Where(c => c.Region == "WA");
    
    waCustomers.ForEach((customer) =>
    {
        Console.WriteLine("Customer {customer.CustomerID}: {customer.CompanyName}");
        customer.Orders.ForEach((order) => 
        {
            Console.WriteLine($"  Order {order.OrderID}: {order.OrderDate}");
        });
    });
} 

//dart
linq4(){
  var customers = customersList(); 
  var waCustomers = customers
      .where((c) => c.region == "WA"); 

  print("Customers from Washington and their orders:");
  waCustomers.forEach((Customer c){
    print("Customer ${c.customerId}: ${c.companyName}");
    c.orders.forEach((o) => print("  Order ${o.orderId}: ${o.orderDate}"));
  });
}

Output

Customers from Washington and their orders:
Customer LAZYK: Lazy K Kountry Store
  Order 10482: 1997-03-21T00:00:00
  Order 10545: 1997-05-22T00:00:00
Customer TRAIH: Trail's Head Gourmet Provisioners
  Order 10574: 1997-06-19T00:00:00
  Order 10577: 1997-06-23T00:00:00
  Order 10822: 1998-01-08T00:00:00
...

linq5: Where - Indexed

//c#
public void Linq5() 
{ 
    var digits = new[] { "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" };

    var shortDigits = digits.Where((digit, index) => digit.Length < index);

    Console.WriteLine("Short digits:");
    shortDigits.ForEach(d => Console.WriteLine($"The word {d} is shorter than its value."));
}

//dart
linq5(){ 
  var digits = ["zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine"]; 
  
  int index=0;
  var shortDigits = digits.where((digit) => digit.length < index++); 
  
  print("Short digits:"); 
  shortDigits.forEach((d) => print("The word $d is shorter than its value."));
}

Output

Short digits:
The word five is shorter than its value.
The word six is shorter than its value.
The word seven is shorter than its value.
The word eight is shorter than its value.
The word nine is shorter than its value.

LINQ - Projection Operators

linq6: Select - Simple 1

//c#
public void Linq6() 
{ 
    var numbers = new[] { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

    var numsPlusOne = numbers
        .Select(n => n + 1);

    Console.WriteLine("Numbers + 1:");
    numsPlusOne.ForEach(Console.WriteLine);
}

//dart
linq6(){
  var numbers = [ 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 ]; 
  
  var numsPlusOne = numbers
    .map((n) => n + 1); 
  
  print("Numbers + 1:"); 
  numsPlusOne.forEach(print);
}

Output

Numbers + 1:
6
5
2
4
10
9
7
8
3
1

linq7: Select - Simple 2

//c#
public void Linq7() 
{ 
    var products = GetProductList();

    var productNames = products
        .Select(p => p.ProductName);

    Console.WriteLine("Product Names:");
    productNames.ForEach(Console.WriteLine);
}

//dart
linq7(){
  var products = productsList(); 
  
  var productNames = products
    .map((p) => p.productName); 
  
  print("Product Names:"); 
  productNames.forEach(print);  
}

Output

Product Names:
Chai
Chang
Aniseed Syrup
Chef Anton's Cajun Seasoning
Chef Anton's Gumbo Mix
...

linq8: Select - Transformation

//c#
public void Linq8() 
{ 
    var numbers = new[] { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
    var strings = new [] { "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" };

    var textNums = numbers
        .Select(n => strings[n]);

    Console.WriteLine("Number strings:");
    textNums.ForEach(Console.WriteLine);
}

//dart
linq8(){
  var numbers = [5, 4, 1, 3, 9, 8, 6, 7, 2, 0]; 
  var strings = ["zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine"]; 
  
  var textNums = numbers
    .map((n) => strings[n]); 
  
  print("Number strings:"); 
  textNums.forEach(print);  
}

Output

Number strings:
five
four
one
three
nine
eight
six
seven
two
zero

linq9: Select - Anonymous Types 1

//c#
public void Linq9() 
{ 
    var words = new[] { "aPPLE", "BlUeBeRrY", "cHeRry" };

    var upperLowerWords = words
        .Select(w => new { Upper = w.ToUpper(), Lower = w.ToLower() });

    upperLowerWords.ForEach(ul => Console.WriteLine($"Uppercase: {ul.Upper}, Lowercase: {ul.Lower}"));
}

//dart
linq9(){
  var words = ["aPPLE", "BlUeBeRrY", "cHeRry"]; 
  
  var upperLowerWords = words 
    .map((w) => { 'Upper': w.toUpperCase(), 'Lower': w.toLowerCase() });
      
  upperLowerWords.forEach((ul) => 
    print("Uppercase: ${ul['Upper']}, Lowercase: ${ul['Lower']}")); 
}

Output

Uppercase: APPLE, Lowercase: apple
Uppercase: BLUEBERRY, Lowercase: blueberry
Uppercase: CHERRY, Lowercase: cherry

linq10: Select - Anonymous Types 2

//c#
public void Linq10() 
{ 
    var numbers = new[] { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
    var strings = new[] { "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" };

    var digitOddEvens = numbers
        .Select(n => new { Digit = strings[n], Even = (n % 2 == 0) });
    
    digitOddEvens.ForEach(d => Console.WriteLine($"The digit {d.Digit} is {(d.Even ? "even" : "odd")}."));
}

//dart
linq10(){
  var numbers = [ 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 ]; 
  var strings = [ "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" ]; 
  
  var digitOddEvens = numbers 
    .map((n) => { 'Digit': strings[n], 'Even': (n % 2 == 0) }); 
      
  digitOddEvens.forEach((d) => 
    print("The digit ${d['Digit']} is ${d['Even'] ? 'even' : 'odd'}.")); 
}

Output

The digit five is odd.
The digit four is even.
The digit one is odd.
The digit three is odd.
The digit nine is odd.
The digit eight is even.
The digit six is even.
The digit seven is odd.
The digit two is even.
The digit zero is even.

linq11: Select - Anonymous Types 3

//c#
public void Linq11() 
{ 
    var products = GetProductList();

    var productInfos = products
        .Select(p => new { p.ProductName, p.Category, Price = p.UnitPrice });

    Console.WriteLine("Product Info:");
    productInfos.ForEach(productInfo => Console.WriteLine($"{productInfo.ProductName} is in the category {productInfo.Category} and costs {productInfo.Price} per unit."));
 }

//dart
linq11(){
  var products = productsList(); 
  
  var productInfos = products 
    .map((p) => { 'ProductName':p.productName, 'Category':p.category, 'Price': p.unitPrice }); 
      
  print("Product Info:"); 
  productInfos.forEach((p) =>
    print("${p['ProductName']} is in the category ${p['Category']} and costs ${p['Price']} per unit."));
}

Output

Product Info:
Chai is in the category Beverages and costs 18.0 per unit.
Chang is in the category Beverages and costs 19.0 per unit.
Aniseed Syrup is in the category Condiments and costs 10.0 per unit.
...

linq12: Select - Indexed

//c#
public void Linq12() 
{ 
    var numbers = new[] { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

    var numsInPlace = numbers
        .Select((num, index) => new { Num = num, InPlace = (num == index) });

    Console.WriteLine("Number: In-place?");
    numsInPlace.ForEach(n => Console.WriteLine($"{n.Num}: {n.InPlace}"));
}

//dart
linq12(){
  var numbers = [ 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 ]; 
  
  int index = 0;
  var numsInPlace = numbers
    .map((num) => { 'Num': num, 'InPlace': (num == index++) }); 
  
  print("Number: In-place?"); 
  numsInPlace.forEach((n) =>
    print("${n['Num']}: ${n['InPlace']}"));
}

Output

Number: In-place?
5: false
4: false
1: false
3: true
9: false
8: false
6: true
7: true
2: false
0: false

linq13: Select - Filtered

//c#
public void Linq13() 
{ 
    var numbers = new []{ 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
    var  digits = new [] { "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" };

    var lowNums = numbers
        .Where(n => n < 5)
        .Select(n => digits[n]);

    Console.WriteLine("Numbers < 5:");
    lowNums.ForEach(Console.WriteLine);

//dart
linq13(){
  var numbers = [ 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 ]; 
  var digits = [ "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" ]; 
  
  var lowNums = numbers 
    .where((n) => n < 5)
    .map((n) => digits[n]); 
  
  print("Numbers < 5:"); 
  lowNums.forEach(print);   
}

Output

Numbers < 5:
four
one
three
two
zero

linq14: SelectMany - Compound from 1

//c#
public void Linq14() 
{ 
    var numbersA = new [] { 0, 2, 4, 5, 6, 8, 9 };
    var numbersB = new []{ 1, 3, 5, 7, 8 };

    var pairs = numbersA
        .SelectMany(a => numbersB, (a, b) => new { a, b })
        .Where(x => x.a < x.b);

    Console.WriteLine("Pairs where a < b:");
    pairs.ForEach(pair => Console.WriteLine("{0} is less than {1}", pair.a, pair.b));
}

//dart
linq14(){
  var numbersA = [ 0, 2, 4, 5, 6, 8, 9 ]; 
  var numbersB = [ 1, 3, 5, 7, 8 ]; 
  
  var pairs = numbersA
    .expand((a) => numbersB
      .where((b) => a < b)
      .map((b) => { 'a':a, 'b':b }));
  
  print("Pairs where a < b:"); 
  pairs.forEach((pair) =>
    print("${pair['a']} is less than ${pair['b']}"));  
}

Output

Pairs where a < b:
0 is less than 1
0 is less than 3
0 is less than 5
0 is less than 7
0 is less than 8
2 is less than 3
2 is less than 5
2 is less than 7
2 is less than 8
4 is less than 5
4 is less than 7
4 is less than 8
5 is less than 7
5 is less than 8
6 is less than 7
6 is less than 8

linq15: SelectMany - Compound from 2

//c#
public void Linq15() 
{ 
    var customers = GetCustomerList();

    var orders = customers
        .SelectMany(customer => customer.Orders, (customer, order) => new { customer, order })
        .Where(x => x.order.Total < 500.00M)
        .Select(x =>  new { x.customer.CustomerID, x.order.OrderID, x.order.Total });

    ObjectDumper.Write(orders);
}

//dart
linq15(){
  var customers = customersList(); 
  
  var orders = customers
    .expand((c) => c.orders
      .where((o) => o.total < 500)
      .map((o) => { 'CustomerId': c.customerId, 'OrderId':o.orderId, 'Total':o.total }));
  
  orders.forEach(print);   
}

Output

{CustomerId: ALFKI, OrderId: 10702, Total: 330.0}
{CustomerId: ALFKI, OrderId: 10952, Total: 471.2}
{CustomerId: ANATR, OrderId: 10308, Total: 88.8}
{CustomerId: ANATR, OrderId: 10625, Total: 479.75}
...

linq16: SelectMany - Compound from 3

//c#
public void Linq16() 
{ 
    var customers = GetCustomerList();

    var orders = customers
        .SelectMany(customer => customer.Orders, (customer, order) => new { customer, order })
        .Where(x => x.order.OrderDate >= new DateTime(1998, 1, 1))
        .Select(x => new { x.customer.CustomerID, x.order.OrderID, x.order.OrderDate });

    ObjectDumper.Write(orders);
}

//dart
linq16(){
  var customers = customersList(); 
  
  var orders = customers
    .expand((c) => c.orders
      .where((o) => o.orderDate.isAfter(new DateTime(1998, 1, 1)))
      .map((o) => { 'CustomerId': c.customerId, 'OrderId':o.orderId, 'OrderDate':o.orderDate }));
  
  orders.forEach(print);   
}

Output

{CustomerId: ALFKI, OrderId: 10835, OrderDate: 1998-01-15 00:00:00.000}
{CustomerId: ALFKI, OrderId: 10952, OrderDate: 1998-03-16 00:00:00.000}
{CustomerId: ALFKI, OrderId: 11011, OrderDate: 1998-04-09 00:00:00.000}
{CustomerId: ANATR, OrderId: 10926, OrderDate: 1998-03-04 00:00:00.000}
{CustomerId: ANTON, OrderId: 10856, OrderDate: 1998-01-28 00:00:00.000}
...

linq17: SelectMany - from Assignment

//c#
public void Linq17() 
{ 
    var customers = GetCustomerList();

    var orders = customers
        .SelectMany(customer => customer.Orders, (customer, order) => new { customer, order })
        .Where(x => x.order.Total >= 2000.00M)
        .Select(x => new { x.customer.CustomerID, x.order.OrderID, x.order.Total });

    ObjectDumper.Write(orders);
}

//dart
linq17(){
  var customers = customersList(); 
  
  var orders = customers
    .expand((c) => c.orders
      .where((o) => o.total >= 2000)
      .map((o) => { 'CustomerId': c.customerId, 'OrderId':o.orderId, 'Total':o.total }));
  
  orders.forEach(print);   
}

Output

{CustomerId: ANTON, OrderId: 10573, Total: 2082.0}
{CustomerId: AROUT, OrderId: 10558, Total: 2142.9}
{CustomerId: AROUT, OrderId: 10953, Total: 4441.25}
{CustomerId: BERGS, OrderId: 10384, Total: 2222.4}
{CustomerId: BERGS, OrderId: 10524, Total: 3192.65}
...

linq18: SelectMany - Multiple from

//c#
public void Linq18() 
{ 
    var customers = GetCustomerList();

    var cutoffDate = new DateTime(1997, 1, 1);

    var orders = customers
        .Where(c => c.Region == "WA")
        .SelectMany(customer => customer.Orders, (customer, order) => new { customer, order })
        .Where(x => x.order.OrderDate >= cutoffDate)
        .Select(x => new { x.customer.CustomerID, x.customer.Region, x.order.OrderID });

    ObjectDumper.Write(orders);
}

//dart
linq18(){
  var customers = customersList(); 

  var cutoffDate = new DateTime(1997, 1, 1); 
  
  var orders = customers
    .where((c) => c.region == "WA")
    .expand((c) => c.orders
      .where((o) => o.orderDate.isAfter(cutoffDate))
      .map((o) => { 'CustomerId': c.customerId, 'OrderId':o.orderId }));
  
  orders.forEach(print);   
}

Output

{CustomerId: LAZYK, OrderId: 10482}
{CustomerId: LAZYK, OrderId: 10545}
{CustomerId: TRAIH, OrderId: 10574}
{CustomerId: TRAIH, OrderId: 10577}
{CustomerId: TRAIH, OrderId: 10822}
{CustomerId: WHITC, OrderId: 10469}
{CustomerId: WHITC, OrderId: 10483}
{CustomerId: WHITC, OrderId: 10504}
{CustomerId: WHITC, OrderId: 10596}
{CustomerId: WHITC, OrderId: 10693}
{CustomerId: WHITC, OrderId: 10696}
{CustomerId: WHITC, OrderId: 10723}
{CustomerId: WHITC, OrderId: 10740}
{CustomerId: WHITC, OrderId: 10861}
{CustomerId: WHITC, OrderId: 10904}
{CustomerId: WHITC, OrderId: 11032}
{CustomerId: WHITC, OrderId: 11066}

linq19: SelectMany - Indexed

//c#
public void Linq19() 
{ 
    var customers = GetCustomerList();

    var customerOrders =
            customers.SelectMany(
                (cust, custIndex) =>
                    cust.Orders.Select(o => $"Customer #{custIndex + 1}) has an order with OrderID {o.OrderID}"));

    ObjectDumper.Write(customerOrders);
}

//dart
linq19(){
  var customers = customersList(); 

  int custIndex = 0;
  var customerOrders = 
    customers.expand((cust){
      custIndex++;
      return cust.orders.map((o) => 
        "Customer #${custIndex} has an order with OrderID ${o.orderId}");
    }); 
    
  customerOrders.forEach(print);   
}

Output

Customer #1 has an order with OrderID 10643
Customer #1 has an order with OrderID 10692
Customer #1 has an order with OrderID 10702
Customer #1 has an order with OrderID 10835
Customer #1 has an order with OrderID 10952
Customer #1 has an order with OrderID 11011
Customer #2 has an order with OrderID 10308
Customer #2 has an order with OrderID 10625
Customer #2 has an order with OrderID 10759
Customer #2 has an order with OrderID 10926
...

LINQ - Partitioning Operators

linq20: Take - Simple

//c#
public void Linq20() 
{ 
    var numbers = new [] { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

    var first3Numbers = numbers.Take(3);

    Console.WriteLine("First 3 numbers:");
    first3Numbers.ForEach(Console.WriteLine);
}

//dart
linq20(){
  var numbers = [ 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 ]; 
  
  var first3Numbers = numbers.take(3); 

  print("First 3 numbers:"); 
  first3Numbers.forEach(print); 
}

Output

First 3 numbers:
5
4
1

linq21: Take - Nested

//c#
public void Linq21()   
{ 
    var customers = GetCustomerList();

    var first3WAOrders = customers
        .Where(c => c.Region == "WA")
        .SelectMany(customer => customer.Orders, (customer, order) => new { customer, order })
        .Select(x => new { x.customer.CustomerID, x.order.OrderID, x.order.OrderDate })
        .Take(3);

    Console.WriteLine("First 3 orders in WA:");
    first3WAOrders.ForEach(ObjectDumper.Write);
}

//dart
linq21(){
  var customers = customersList(); 
  
  var first3WAOrders = customers
    .where((c) => c.region == "WA")
    .expand((c) => c.orders
      .map((o) => { 'CustomerId': c.customerId, 'OrderId':o.orderId, 'OrderDate':o.orderDate }))
    .take(3);
  
  print("First 3 orders in WA:");
  first3WAOrders.forEach(print);
}

Output

First 3 orders in WA:
{CustomerId: LAZYK, OrderId: 10482, OrderDate: 1997-03-21 00:00:00.000}
{CustomerId: LAZYK, OrderId: 10545, OrderDate: 1997-05-22 00:00:00.000}
{CustomerId: TRAIH, OrderId: 10574, OrderDate: 1997-06-19 00:00:00.000}

linq22: Skip - Simple

//c#
public void Linq22() 
{ 
    var numbers = new []{ 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

    var allButFirst4Numbers = numbers.Skip(4);

    Console.WriteLine("All but first 4 numbers:");
    allButFirst4Numbers.ForEach(Console.WriteLine);
}

//dart
linq22(){
  var numbers = [ 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 ]; 
  var allButFirst4Numbers = numbers.skip(4); 

  print("All but first 4 numbers:");
  allButFirst4Numbers.forEach(print);
}

Output

All but first 4 numbers:
9
8
6
7
2
0

linq23: Skip - Nested

//c#
public void Linq23()   
{ 
    var customers = GetCustomerList();

    var waOrders = customers
        .Where(c => c.Region == "WA")
        .SelectMany(customer => customer.Orders, (customer, order) => new { customer, order })
        .Select(x => new { x.customer.CustomerID, x.order.OrderID, x.order.OrderDate });

    var allButFirst2Orders = waOrders.Skip(2);

    Console.WriteLine("All but first 2 orders in WA:");
    allButFirst2Orders.ForEach(ObjectDumper.Write);
}

//dart
linq23(){
  var customers = customersList(); 
  
  var waOrders = customers
    .where((c) => c.region == "WA")
    .expand((c) => c.orders
      .map((o) => { 'CustomerId': c.customerId, 'OrderId':o.orderId, 'OrderDate':o.orderDate }));

  var allButFirst2Orders = waOrders.skip(2);
  
  print("All but first 2 orders in WA:");
  allButFirst2Orders.forEach(print);
}

Output

All but first 2 orders in WA:
{CustomerId: TRAIH, OrderId: 10574, OrderDate: 1997-06-19 00:00:00.000}
{CustomerId: TRAIH, OrderId: 10577, OrderDate: 1997-06-23 00:00:00.000}
{CustomerId: TRAIH, OrderId: 10822, OrderDate: 1998-01-08 00:00:00.000}
{CustomerId: WHITC, OrderId: 10269, OrderDate: 1996-07-31 00:00:00.000}
{CustomerId: WHITC, OrderId: 10344, OrderDate: 1996-11-01 00:00:00.000}
{CustomerId: WHITC, OrderId: 10469, OrderDate: 1997-03-10 00:00:00.000}
{CustomerId: WHITC, OrderId: 10483, OrderDate: 1997-03-24 00:00:00.000}
{CustomerId: WHITC, OrderId: 10504, OrderDate: 1997-04-11 00:00:00.000}
{CustomerId: WHITC, OrderId: 10596, OrderDate: 1997-07-11 00:00:00.000}
{CustomerId: WHITC, OrderId: 10693, OrderDate: 1997-10-06 00:00:00.000}
{CustomerId: WHITC, OrderId: 10696, OrderDate: 1997-10-08 00:00:00.000}
{CustomerId: WHITC, OrderId: 10723, OrderDate: 1997-10-30 00:00:00.000}
{CustomerId: WHITC, OrderId: 10740, OrderDate: 1997-11-13 00:00:00.000}
{CustomerId: WHITC, OrderId: 10861, OrderDate: 1998-01-30 00:00:00.000}
{CustomerId: WHITC, OrderId: 10904, OrderDate: 1998-02-24 00:00:00.000}
{CustomerId: WHITC, OrderId: 11032, OrderDate: 1998-04-17 00:00:00.000}
{CustomerId: WHITC, OrderId: 11066, OrderDate: 1998-05-01 00:00:00.000}

linq24: TakeWhile - Simple

//c#
public void Linq24() 
{ 
    var numbers = new[] { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

    var firstNumbersLessThan6 = numbers.TakeWhile(n => n < 6);

    Console.WriteLine("First numbers less than 6:");
    firstNumbersLessThan6.ForEach(Console.WriteLine);
}

//dart
linq24(){
  var numbers = [ 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 ]; 
  
  var firstNumbersLessThan6 = numbers.takeWhile((n) => n < 6); 
  
  print("First numbers less than 6:"); 
  firstNumbersLessThan6.forEach(print);
}

Output

First numbers less than 6:
5
4
1
3

linq25: TakeWhile - Indexed

//c#
public void Linq25() 
{ 
    var numbers = new [] { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

    var firstSmallNumbers = numbers.TakeWhile((n, index) => n >= index);

    Console.WriteLine("First numbers not less than their position:");
    firstSmallNumbers.ForEach(Console.WriteLine);
}

//dart
linq25(){
  var numbers = [ 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 ]; 
  
  int index = 0;
  var firstSmallNumbers = numbers.takeWhile((n) => n >= index++); 

  print("First numbers not less than their position:"); 
  firstSmallNumbers.forEach(print);
}

Output

First numbers not less than their position:
5
4

linq26: SkipWhile - Simple

//c#
public void Linq26() 
{ 
    var numbers = new [] { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

    var allButFirst3Numbers = numbers.SkipWhile(n => n % 3 != 0);

    Console.WriteLine("All elements starting from first element divisible by 3:");
    allButFirst3Numbers.ForEach(Console.WriteLine);
}

//dart
linq26(){
  var numbers = [ 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 ]; 
  
  var allButFirst3Numbers = numbers.skipWhile((n) => n % 3 != 0); 
  print("All elements starting from first element divisible by 3:"); 
  allButFirst3Numbers.forEach(print);
}

Output

All elements starting from first element divisible by 3:
3
9
8
6
7
2
0

linq27: SkipWhile - Indexed

//c#
public void Linq27() 
{ 
    var numbers = new [] { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

    var laterNumbers = numbers.SkipWhile((n, index) => n >= index);

    Console.WriteLine("All elements starting from first element less than its position:");
    laterNumbers.ForEach(Console.WriteLine);
}

//dart
linq27(){
  var numbers = [ 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 ]; 
  
  int index = 0;
  var laterNumbers = numbers.skipWhile((n) => n >= index++); 
  
  print("All elements starting from first element less than its position:"); 
  laterNumbers.forEach(print);
}

Output

All elements starting from first element less than its position:
1
3
9
8
6
7
2
0

LINQ - Ordering Operators

C# utils added

// No utils reuired, use built in comparer
StringComparer.CurrentCultureIgnoreCase

Dart utils added

wrap(value, fn(x)) => fn(value);

order(List seq, {Comparator by, List<Comparator> byAll, on(x), List<Function> onAll}) =>
  by != null ? 
    (seq..sort(by)) 
  : byAll != null ?
    (seq..sort((a,b) => byAll
      .firstWhere((compare) => compare(a,b) != 0, orElse:() => (x,y) => 0)(a,b)))
  : on != null ? 
    (seq..sort((a,b) => on(a).compareTo(on(b)))) 
  : onAll != null ?
    (seq..sort((a,b) =>
      wrap(onAll.firstWhere((_on) => _on(a).compareTo(_on(b)) != 0, orElse:() => (x) => 0),
        (_on) => _on(a).compareTo(_on(b)) 
    ))) 
  : (seq..sort()); 

caseInsensitiveComparer(a,b) => 
  a.toUpperCase().compareTo(b.toUpperCase());

linq28: OrderBy - Simple 1

//c#
public void Linq28() 
{ 
    var words = new [] { "cherry", "apple", "blueberry" };

    var sortedWords = words.OrderBy(w => w);

    Console.WriteLine("The sorted list of words:");
    sortedWords.ForEach(Console.WriteLine);
}

//dart
linq28(){
  var words = [ "cherry", "apple", "blueberry" ]; 
  
  var sortedWords = order(words);
  
  print("The sorted list of words:"); 
  sortedWords.forEach(print);
}

Output

The sorted list of words:
apple
blueberry
cherry

linq29: OrderBy - Simple 2

//c#
public void Linq29() 
{ 
    var words = new [] { "cherry", "apple", "blueberry" };

    var sortedWords = words.OrderBy(w => w.Length);

    Console.WriteLine("The sorted list of words (by length):"); 
    sortedWords.ForEach(Console.WriteLine);
}

//dart
linq29(){
  var words = [ "cherry", "apple", "blueberry" ]; 
  
  var sortedWords = order(words, on:(a) => a.length);
  
  print("The sorted list of words (by length):"); 
  sortedWords.forEach(print);
}

Output

The sorted list of words (by length):
apple
cherry
blueberry

linq30: OrderBy - Simple 3

//c#
public void Linq30() 
{ 
    var products = GetProductList();

    var sortedProducts = products.OrderBy(p => p.ProductName);

    ObjectDumper.Write(sortedProducts);
}

//dart
linq30(){
  var products = productsList(); 
  
  var sortedProducts = order(products, on:(a) => a.productName);
  
  sortedProducts.forEach(print);
}

Output

{productId: 17, productName: Alice Mutton, category: Meat/Poultry, unitPrice: 39.0, unitsInStock: 0}
{productId: 3, productName: Aniseed Syrup, category: Condiments, unitPrice: 10.0, unitsInStock: 13}
{productId: 40, productName: Boston Crab Meat, category: Seafood, unitPrice: 18.4, unitsInStock: 123}
{productId: 60, productName: Camembert Pierrot, category: Dairy Products, unitPrice: 34.0, unitsInStock: 19}
{productId: 18, productName: Carnarvon Tigers, category: Seafood, unitPrice: 62.5, unitsInStock: 42}
...

linq31: OrderBy - Comparer

//c#
public void Linq31() 
{ 
    var words = new [] { "aPPLE", "AbAcUs", "bRaNcH", "BlUeBeRrY", "ClOvEr", "cHeRry" }; 

    var sortedWords = words.OrderBy(a => a, StringComparer.CurrentCultureIgnoreCase); 

    ObjectDumper.Write(sortedWords); 
} 

//dart
linq31(){
  var words = [ "aPPLE", "AbAcUs", "bRaNcH", "BlUeBeRrY", "ClOvEr", "cHeRry" ]; 
  
  var sortedWords = order(words, by:caseInsensitiveComparer); 
  
  sortedWords.forEach(print);
}

Output

AbAcUs
aPPLE
BlUeBeRrY
bRaNcH
cHeRry
ClOvEr

linq32: OrderByDescending - Simple 1

//c#
public void Linq32() 
{ 
    var doubles = new[]{ 1.7, 2.3, 1.9, 4.1, 2.9 };

    var sortedDoubles = doubles.OrderByDescending(d => d);

    Console.WriteLine("The doubles from highest to lowest:");
    sortedDoubles.ForEach(Console.WriteLine);
}

//dart
linq32(){
  var doubles = [ 1.7, 2.3, 1.9, 4.1, 2.9 ]; 
  
  var sortedDoubles = order(doubles).reversed; 
  
  print("The doubles from highest to lowest:");   
  sortedDoubles.forEach(print);
}

Output

The doubles from highest to lowest:
4.1
2.9
2.3
1.9
1.7

linq33: OrderByDescending - Simple 2

//c#
public void Linq33() 
{ 
    var products = GetProductList();

    var sortedProducts = products.OrderByDescending(p => p.UnitsInStock);

    ObjectDumper.Write(sortedProducts);
}

//dart
linq33(){
  var products = productsList(); 
  
  var sortedProducts = order(products, on:(a) => a.unitsInStock).reversed; 
  
  sortedProducts.forEach(print);
}

Output

{productId: 75, productName: Rh�nbr�u Klosterbier, category: Beverages, unitPrice: 7.75, unitsInStock: 125}
{productId: 40, productName: Boston Crab Meat, category: Seafood, unitPrice: 18.4, unitsInStock: 123}
{productId: 6, productName: Grandma's Boysenberry Spread, category: Condiments, unitPrice: 25.0, unitsInStock: 120}
{productId: 55, productName: P�t� chinois, category: Meat/Poultry, unitPrice: 24.0, unitsInStock: 115}
{productId: 61, productName: Sirop d'�rable, category: Condiments, unitPrice: 28.5, unitsInStock: 113}
...

linq34: OrderByDescending - Comparer

//c#
public void Linq34() 
{ 
    var words = new [] { "aPPLE", "AbAcUs", "bRaNcH", "BlUeBeRrY", "ClOvEr", "cHeRry" };

    var sortedWords = words.OrderByDescending(a => a, StringComparer.CurrentCultureIgnoreCase); 

    ObjectDumper.Write(sortedWords);
} 

//dart
linq34(){
  var words = [ "aPPLE", "AbAcUs", "bRaNcH", "BlUeBeRrY", "ClOvEr", "cHeRry" ]; 
  
  var sortedWords = order(words, by:caseInsensitiveComparer).reversed;
  
  sortedWords.forEach(print);
}

Output

ClOvEr
cHeRry
bRaNcH
BlUeBeRrY
aPPLE
AbAcUs

linq35: ThenBy - Simple

//c#
public void Linq35() 
{ 
    var digits = new [] { "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" };

    var sortedDigits = digits
        .OrderBy(d => d.Length)
        .ThenBy(d => d);

    Console.WriteLine("Sorted digits:");
    sortedDigits.ForEach(Console.WriteLine);
}

//dart
linq35(){
  var digits = [ "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" ]; 
  
  var sortedDigits = order(digits, onAll:[(a) => a.length, (a) => a]);
  
  print("Sorted digits:"); 
  sortedDigits.forEach(print);
}

Output

Sorted digits:
one
six
two
five
four
nine
zero
eight
seven
three

linq36: ThenBy - Comparer

//c#
public void Linq36() 
{ 
    var words = new [] { "aPPLE", "AbAcUs", "bRaNcH", "BlUeBeRrY", "ClOvEr", "cHeRry" };

    var sortedWords = words
        .OrderBy(a => a.Length)
        .ThenBy(a => a, StringComparer.CurrentCultureIgnoreCase);

    ObjectDumper.Write(sortedWords);
} 

//dart
linq36(){
  var words = [ "aPPLE", "AbAcUs", "bRaNcH", "BlUeBeRrY", "ClOvEr", "cHeRry" ]; 
  
  var sortedWords = order(words, byAll:[(a,b) => a.length.compareTo(b.length), caseInsensitiveComparer]);
  
  sortedWords.forEach(print);
}

Output

aPPLE
AbAcUs
bRaNcH
cHeRry
ClOvEr
BlUeBeRrY

linq37: ThenByDescending - Simple

//c#
public void Linq37() 
{ 
    List<Product> products = GetProductList(); 

    var sortedProducts = products
        .OrderBy(p => p.Category)
        .ThenByDescending(p => p.UnitPrice);

    ObjectDumper.Write(sortedProducts); 
}

//dart
linq37(){
  var products = productsList(); 

  var sortedProducts = order(products, onAll:[(a) => a.category, (a) => a.unitPrice * -1]);
  
  sortedProducts.forEach(print);
}

Output

{productId: 38, productName: C�te de Blaye, category: Beverages, unitPrice: 263.5, unitsInStock: 17}
{productId: 43, productName: Ipoh Coffee, category: Beverages, unitPrice: 46.0, unitsInStock: 17}
{productId: 2, productName: Chang, category: Beverages, unitPrice: 19.0, unitsInStock: 17}
{productId: 76, productName: Lakkalik��ri, category: Beverages, unitPrice: 18.0, unitsInStock: 57}
{productId: 39, productName: Chartreuse verte, category: Beverages, unitPrice: 18.0, unitsInStock: 69}
{productId: 1, productName: Chai, category: Beverages, unitPrice: 18.0, unitsInStock: 39}
{productId: 35, productName: Steeleye Stout, category: Beverages, unitPrice: 18.0, unitsInStock: 20}
{productId: 70, productName: Outback Lager, category: Beverages, unitPrice: 15.0, unitsInStock: 15}
{productId: 34, productName: Sasquatch Ale, category: Beverages, unitPrice: 14.0, unitsInStock: 111}
...

linq38: ThenByDescending - Comparer

//c#
public void Linq38() 
{ 
    var words = new [] { "aPPLE", "AbAcUs", "bRaNcH", "BlUeBeRrY", "ClOvEr", "cHeRry" };

    var sortedWords = words
        .OrderBy(a => a.Length)
        .ThenByDescending(a => a, StringComparer.CurrentCultureIgnoreCase);

    ObjectDumper.Write(sortedWords);
} 

//dart
linq38(){
  var words = [ "aPPLE", "AbAcUs", "bRaNcH", "BlUeBeRrY", "ClOvEr", "cHeRry" ]; 
  
  var sortedWords = order(words, 
    byAll:[(a,b) => a.length.compareTo(b.length), (a,b) => caseInsensitiveComparer(b,a)]); 

  sortedWords.forEach(print);
}

Output

aPPLE
ClOvEr
cHeRry
bRaNcH
AbAcUs
BlUeBeRrY

linq39: Reverse

//c#
public void Linq39() 
{ 
    var digits = new [] { "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" };

    var reversedIDigits = digits
        .Where(d => d[1] == 'i')
        .Reverse();

    Console.WriteLine("A backwards list of the digits with a second character of 'i':");
    reversedIDigits.ForEach(Console.WriteLine);
}

//dart
linq39(){
  var digits = [ "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" ]; 
  
  var reversedIDigits = digits
    .where((d) => d[1] == 'i')
    .toList()
    .reversed; 
  
  print("A backwards list of the digits with a second character of 'i':");
  reversedIDigits.forEach(print);
}

Output

A backwards list of the digits with a second character of 'i':
nine
eight
six
five

LINQ - Grouping Operators

C# utils added

public class AnagramEqualityComparer : IEqualityComparer<string> 
{ 
    public bool Equals(string x, string y) 
    { 
        return getCanonicalString(x) == getCanonicalString(y); 
    } 
  
    public int GetHashCode(string obj) 
    { 
        return getCanonicalString(obj).GetHashCode(); 
    } 
  
    private string getCanonicalString(string word) 
    { 
        char[] wordChars = word.ToCharArray(); 
        Array.Sort<char>(wordChars); 
        return new string(wordChars); 
    } 
} 

Dart utils added

anagramEqualityComparer(a, b) => 
  new String.fromCharCodes(orderBy(a.codeUnits.toList()))
  .compareTo(new String.fromCharCodes(orderBy(b.codeUnits.toList())));

List<Group> group(Iterable seq, {by(x):null, Comparator matchWith:null, valuesAs(x):null}){
  var ret = [];
  var map = new Map<dynamic, Group>();
  seq.forEach((x){
    var val = by(x);
    var key = matchWith != null
      ? map.keys.firstWhere((k) => matchWith(val, k) == 0, orElse:() => val)
      : val;
    
    if (!map.containsKey(key))
      map[key] = new Group(val);
    
    if (valuesAs != null)
      x = valuesAs(x);
    
    map[key].add(x);
  });
  return map.values.toList();
}

class Group extends IterableBase {
  var key;
  List _list;
  Group(this.key) : _list = [];

  get iterator => _list.iterator;
  void add(e) => _list.add(e);  
  get values => _list;
}

linq40: GroupBy - Simple 1

//c#
public void Linq40() 
{ 
    var numbers = new[] { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 }; 

    var numberGroups = numbers
        .GroupBy(n => n % 5)
        .Select(x => new {Remainder = x.Key, Numbers = x});

    numberGroups.ForEach((g) => 
    {
            Console.WriteLine("Numbers with a remainder of {0} when divided by 5:", g.Remainder);
            g.Numbers.ForEach(Console.WriteLine);
    });
}

//dart
linq40(){
  var numbers = [ 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 ]; 
  
  var numberGroups = group(numbers, by:(n) => n % 5)
    .map((g) => {'Remainder':g.key, 'Numbers':g});
      
  numberGroups.forEach((g){
    print("Numbers with a remainder of ${g['Remainder']} when divided by 5:"); 
    g['Numbers'].forEach(print);
  });
}

Output

Numbers with a remainder of 0 when divided by 5:
5
0
Numbers with a remainder of 1 when divided by 5:
1
6
Numbers with a remainder of 2 when divided by 5:
7
2
Numbers with a remainder of 3 when divided by 5:
3
8
Numbers with a remainder of 4 when divided by 5:
4
9

linq41: GroupBy - Simple 2

//c#
public void Linq41() 
{ 
    var words = new [] { "blueberry", "chimpanzee", "abacus", "banana", "apple", "cheese" }; 

    var wordGroups = words
        .GroupBy(w => w[0])
        .Select(g => new { FirstLetter = g.Key, Words = g });

    wordGroups.ForEach((g) => 
    {
        Console.WriteLine($"Words that start with the letter '{g.FirstLetter}':");
        g.Words.ForEach(Console.WriteLine);
    });
}

linq41(){
  var words = [ "blueberry", "chimpanzee", "abacus", "banana", "apple", "cheese" ]; 
  
  var wordGroups = group(words, by:(w) => w[0])
    .map((g) => { 'FirstLetter': g.key, 'Words': g }); 
      
  wordGroups.forEach((g){
    print("Words that start with the letter '${g['FirstLetter']}':"); 
    g['Words'].forEach(print);
  });
}

Output

//dart
Words that start with the letter 'c':
chimpanzee
cheese
Words that start with the letter 'a':
abacus
apple
Words that start with the letter 'b':
blueberry
banana

linq42: GroupBy - Simple 3

//c#
public void Linq42() 
{ 
    var products = GetProductList(); 
    
    var orderGroups = products
        .GroupBy(p => p.Category)
        .Select(g => new { Category = g.Key, Products = g }); 

    ObjectDumper.Write(orderGroups, 1); 
} 

//dart
linq42(){
  var products = productsList(); 
  
  var orderGroups = group(products, by:(p) => p.category)
    .map((g) => { 'Category': g.key, 'Products': g });
 
  orderGroups.forEach(print);
}

Output

{Category: Dairy Products, Products: {{productId: 11, productName: Queso Cabrales, category: Dairy Products, unitPrice: 21.0, unitsInStock: 22}, {productId: 12, productName: Queso Manchego La Pastora, category: Dairy Products, unitPrice: 38.0, unitsInStock: 86}, {productId: 31, productName: Gorgonzola Telino, category: Dairy Products, unitPrice: 12.5, unitsInStock: 0}, {productId: 32, productName: Mascarpone Fabioli, category: Dairy Products, unitPrice: 32.0, unitsInStock: 9}, {productId: 33, productName: Geitost, category: Dairy Products, unitPrice: 2.5, unitsInStock: 112}, {productId: 59, productName: Raclette Courdavault, category: Dairy Products, unitPrice: 55.0, unitsInStock: 79}, {productId: 60, productName: Camembert Pierrot, category: Dairy Products, unitPrice: 34.0, unitsInStock: 19}, {productId: 69, productName: Gudbrandsdalsost, category: Dairy Products, unitPrice: 36.0, unitsInStock: 26}, {productId: 71, productName: Flotemysost, category: Dairy Products, unitPrice: 21.5, unitsInStock: 26}, {productId: 72, productName: Mozzarella di Giovanni, category: Dairy Products, unitPrice: 34.8, unitsInStock: 14}}}
{Category: Grains/Cereals, Products: {{productId: 22, productName: Gustaf's Kn�ckebr�d, category: Grains/Cereals, unitPrice: 21.0, unitsInStock: 104}, {productId: 23, productName: Tunnbr�d, category: Grains/Cereals, unitPrice: 9.0, unitsInStock: 61}, {productId: 42, productName: Singaporean Hokkien Fried Mee, category: Grains/Cereals, unitPrice: 14.0, unitsInStock: 26}, {productId: 52, productName: Filo Mix, category: Grains/Cereals, unitPrice: 7.0, unitsInStock: 38}, {productId: 56, productName: Gnocchi di nonna Alice, category: Grains/Cereals, unitPrice: 38.0, unitsInStock: 21}, {productId: 57, productName: Ravioli Angelo, category: Grains/Cereals, unitPrice: 19.5, unitsInStock: 36}, {productId: 64, productName: Wimmers gute Semmelkn�del, category: Grains/Cereals, unitPrice: 33.25, unitsInStock: 22}}}

linq43: GroupBy - Nested

//c#
public void Linq43() 
{ 
    var customers = GetCustomerList(); 

    var customerOrderGroups = customers
        .Select(c => new 
        {
            c.CompanyName,
            YearGroups = 
            (
                c.Orders
                    .GroupBy(y => y.OrderDate.Year)
                    .Select(YearGroup => new 
                    {
                        Year = YearGroup.Key,
                        MonthGroups = 
                        (
                            YearGroup
                            .GroupBy(m =>  m.OrderDate.Month)
                            .Select(MonthGroup => new
                            {
                                Month = MonthGroup.Key, Orders = MonthGroup
                            })

                        )
                    })
            )
        });
        
    ObjectDumper.Write(customerOrderGroups, 3); 
} 

//dart
linq43(){
  var customers = customersList(); 
  
  var customerOrderGroups = customers
      .map((c) => {
        'CompanyName': c.companyName, 
        'YearGroups': group(c.orders, by:(o) => o.orderDate.year)
          .map((yg) => {
            'Year': yg.key, 
            'MonthGroups': group(yg, by:(o) => o.orderDate.month)
              .map((mg) => { 'Month': mg.key, 'Orders': mg }) 
          })
      });

  customerOrderGroups.forEach(print);
}

Output

{CompanyName: Alfreds Futterkiste, YearGroups: {{Year: 1997, MonthGroups: {{Month: 8, Orders: {{orderId: 10643, orderDate: 1997-08-25 00:00:00.000, total: 814.5}}}, {Month: 10, Orders: {{orderId: 10692, orderDate: 1997-10-03 00:00:00.000, total: 878.0}, {orderId: 10702, orderDate: 1997-10-13 00:00:00.000, total: 330.0}}}}}, {Year: 1998, MonthGroups: {{Month: 1, Orders: {{orderId: 10835, orderDate: 1998-01-15 00:00:00.000, total: 845.8}}}, {Month: 3, Orders: {{orderId: 10952, orderDate: 1998-03-16 00:00:00.000, total: 471.2}}}, {Month: 4, Orders: {{orderId: 11011, orderDate: 1998-04-09 00:00:00.000, total: 933.5}}}}}}}
{CompanyName: Ana Trujillo Emparedados y helados, YearGroups: {{Year: 1996, MonthGroups: {{Month: 9, Orders: {{orderId: 10308, orderDate: 1996-09-18 00:00:00.000, total: 88.8}}}}}, {Year: 1997, MonthGroups: {{Month: 8, Orders: {{orderId: 10625, orderDate: 1997-08-08 00:00:00.000, total: 479.75}}}, {Month: 11, Orders: {{orderId: 10759, orderDate: 1997-11-28 00:00:00.000, total: 320.0}}}}}, {Year: 1998, MonthGroups: {{Month: 3, Orders: {{orderId: 10926, orderDate: 1998-03-04 00:00:00.000, total: 514.4}}}}}}}

linq44: GroupBy - Comparer

//c#
public void Linq44() 
{ 
    var anagrams = new [] { "from    ", " salt", " earn ", "  last   ", " near ", " form  " }; 
    var orderGroups = anagrams
        .GroupBy(w => w.Trim(), new AnagramEqualityComparer());

    ObjectDumper.Write(orderGroups, 1); 
} 

//dart
linq44(){
  var anagrams = [ "from   ", " salt", " earn ", "  last   ", " near ", " form  " ]; 
  
  var orderGroups = group(anagrams, by:(w) => w.trim(), matchWith:anagramEqualityComparer); 
  
  orderGroups.forEach((x) => print(x.values)); 
}

Output

[ salt,   last   ]
[ earn ,  near ]
[from   ,  form  ]

linq45: GroupBy - Comparer, Mapped

//c#
public void Linq45() 
{ 
    var anagrams = new [] { "from   ", " salt", " earn ", "  last   ", " near ", " form  " }; 

    var orderGroups = anagrams.GroupBy( 
                w => w.Trim(),
                a => a.ToUpper(), 
                new AnagramEqualityComparer() 
                ); 

    ObjectDumper.Write(orderGroups, 1); 
} 

//dart
linq45(){
  var anagrams = [ "from   ", " salt", " earn ", "  last   ", " near ", " form  " ]; 
  
  var orderGroups = group(anagrams, 
    by: (w) => w.trim(), 
    matchWith: anagramEqualityComparer, 
    valuesAs: (w) => w.toUpperCase()); 
  
  orderGroups.forEach((x) => print(x.values)); 
}

Output

[ SALT,   LAST   ]
[ EARN ,  NEAR ]
[FROM   ,  FORM  ]

LINQ - Set Operators

linq46: Distinct - 1

//c#
public void Linq46() 
{ 
    int[] factorsOf300 = { 2, 2, 3, 5, 5 };

    var uniqueFactors = factorsOf300.Distinct();

    Console.WriteLine("Prime factors of 300:");
    uniqueFactors.ForEach(Console.WriteLine); 
}

//dart
linq46(){
  var factorsOf300 = [ 2, 2, 3, 5, 5 ]; 
  
  var uniqueFactors = factorsOf300.toSet(); 

  print("Prime factors of 300:");
  uniqueFactors.forEach(print);
}

Output

Prime factors of 300:
2
3
5

linq47: Distinct - 2

//c#
public void Linq47() 
{ 
    var products = GetProductList();

    var categoryNames = products
        .Select(p => p.Category)
        .Distinct();

    Console.WriteLine("Category names:");
    categoryNames.ForEach(Console.WriteLine);
}

//dart
linq47(){
  var products = productsList(); 
  
  var categoryNames = products 
    .map((p) => p.category)
    .toSet(); 
  
  print("Category names:"); 
  categoryNames.forEach(print);
}

Output

Category names:
Dairy Products
Grains/Cereals
Confections
Seafood
Condiments
Meat/Poultry
Produce
Beverages

linq48: Union - 1

//c#
public void Linq48() 
{ 
    int[] numbersA = { 0, 2, 4, 5, 6, 8, 9 };
    int[] numbersB = { 1, 3, 5, 7, 8 };

    var uniqueNumbers = numbersA.Union(numbersB);

    Console.WriteLine("Unique numbers from both arrays:");
    uniqueNumbers.ForEach(Console.WriteLine);
}

//dart
linq48(){
  var numbersA = [ 0, 2, 4, 5, 6, 8, 9 ]; 
  var numbersB = [ 1, 3, 5, 7, 8 ]; 
  
  var uniqueNumbers = numbersA.toSet().union(numbersB.toSet()); 
  
  print("Unique numbers from both arrays:"); 
  uniqueNumbers.forEach(print);
}

Output

Unique numbers from both arrays:
0
1
2
3
4
5
6
7
8
9

linq49: Union - 2

//c#
public void Linq49() 
{ 
    var products = GetProductList();
    var customers = GetCustomerList();

    var productFirstChars = products
        .Select(p => p.ProductName[0]);
    var customerFirstChars = customers
        .Select(c => c.CompanyName[0]);

    var uniqueFirstChars = productFirstChars.Union(customerFirstChars);

    Console.WriteLine("Unique first letters from Product names and Customer names:");
    uniqueFirstChars.ForEach(Console.WriteLine);
}

//dart
linq49(){
  var products = productsList(); 
  var customers = customersList(); 
  
  var productFirstChars = products 
    .map((p) => p.productName[0]); 
  var customerFirstChars = customers
    .map((c) => c.companyName[0]); 
  
  var uniqueFirstChars = productFirstChars.toSet().union(customerFirstChars.toSet()); 
  
  print("Unique first letters from Product names and Customer names:"); 
  uniqueFirstChars.forEach(print);
}

Output

Unique first letters from Product names and Customer names:
S
F
T
N
K
E
V
Z
Q
M
C
L
A
J
W
P
B
O
H
D
R
I
G
U

linq50: Intersect - 1

//c#
public void Linq50() 
{ 
    int[] numbersA = { 0, 2, 4, 5, 6, 8, 9 };
    int[] numbersB = { 1, 3, 5, 7, 8 };

    var commonNumbers = numbersA.Intersect(numbersB);

    Console.WriteLine("Common numbers shared by both arrays:");
    commonNumbers.ForEach(Console.WriteLine);
}

//dart
linq50(){
  var numbersA = [ 0, 2, 4, 5, 6, 8, 9 ]; 
  var numbersB = [ 1, 3, 5, 7, 8 ]; 
  
  var commonNumbers = numbersA.toSet().intersection(numbersB.toSet()); 
  
  print("Common numbers shared by both arrays:"); 
  commonNumbers.forEach(print);
}

Output

Common numbers shared by both arrays:
8
5

linq51: Intersect - 2

//c#
public void Linq51() 
{ 
    var products = GetProductList();
    var customers = GetCustomerList();

    var productFirstChars = products
        .Select(p => p.ProductName[0]);
    var customerFirstChars = customers
        .Select(c => c.CompanyName[0]);

    var commonFirstChars = productFirstChars.Intersect(customerFirstChars);

    Console.WriteLine("Common first letters from Product names and Customer names:");
    commonFirstChars.ForEach(Console.WriteLine);
}

//dart
linq51(){
  var products = productsList(); 
  var customers = customersList(); 
  
  var productFirstChars = products 
    .map((p) => p.productName[0]); 
  var customerFirstChars = customers
    .map((c) => c.companyName[0]); 
  
  var commonFirstChars = productFirstChars.toSet().intersection(customerFirstChars.toSet()); 
  
  print("Common first letters from Product names and Customer names:"); 
  commonFirstChars.forEach(print);
}

Output

Common first letters from Product names and Customer names:
F
S
T
N
K
E
V
Q
M
C
L
A
O
W
P
B
I
G
R

linq52: Except - 1

//c#
public void Linq52() 
{ 
    int[] numbersA = { 0, 2, 4, 5, 6, 8, 9 };
    int[] numbersB = { 1, 3, 5, 7, 8 };

    var aOnlyNumbers = numbersA.Except(numbersB);

    Console.WriteLine("Numbers in first array but not second array:");
    aOnlyNumbers.ForEach(Console.WriteLine);
}

//dart
linq52(){
  var numbersA = [ 0, 2, 4, 5, 6, 8, 9 ]; 
  var numbersB = [ 1, 3, 5, 7, 8 ]; 
  
  var aOnlyNumbers = numbersA.toSet().difference(numbersB.toSet()); 
  
  print("Numbers in first array but not second array:"); 
  aOnlyNumbers.forEach(print);
}

Output

Numbers in first array but not second array:
0
9
2
4
6

linq53: Except - 2

//c#
public void Linq53() 
{ 
    var products = GetProductList();
    var customers = GetCustomerList();

    var productFirstChars = products
        .Select(p => p.ProductName[0]);
    var customerFirstChars = customers
        .Select(c => c.CompanyName[0]);

    var productOnlyFirstChars = productFirstChars.Except(customerFirstChars);

    Console.WriteLine("First letters from Product names, but not from Customer names:");
    productOnlyFirstChars.ForEach(Console.WriteLine);
}

//dart
linq53(){
  var products = productsList(); 
  var customers = customersList(); 
  
  var productFirstChars = products 
    .map((p) => p.productName[0]); 
  var customerFirstChars = customers
    .map((c) => c.companyName[0]); 
  
  var productOnlyFirstChars = productFirstChars.toSet().difference(customerFirstChars.toSet()); 
  
  print("First letters from Product names, but not from Customer names:"); 
  productOnlyFirstChars.forEach(print);
}

Output

First letters from Product names, but not from Customer names:
Z
J
U

LINQ - Conversion Operators

Dart utils added

toMap(List seq, f(x)){
  var map = {};
  seq.forEach((x) => map[f(x)] = x);
  return map;
}

ofType(List seq, type) =>
  seq.where((x) => reflect(x).type.qualifiedName == reflectClass(type).qualifiedName);

linq54: ToArray

//c#
public void Linq54() 
{ 
    double[] doubles = { 1.7, 2.3, 1.9, 4.1, 2.9 };

    var sortedDoubles = doubles.OrderByDescending(d => d);
        
    var doublesArray = sortedDoubles.ToArray();

    Console.WriteLine("Every other double from highest to lowest:");
    for (int d = 0; d < doublesArray.Length; d += 2)
    {
        Console.WriteLine(doublesArray[d]);
    }
}

//dart
linq54(){
  var doubles = [ 1.7, 2.3, 1.9, 4.1, 2.9 ]; 
  
  var sortedDoubles = order(doubles).reversed;

  var doublesArray = sortedDoubles.toList(growable:false); 
  
  print("Every other double from highest to lowest:"); 
  for (int d = 0; d < doublesArray.length; d += 2){ 
    print(doublesArray[d]); 
  } 
}

Output

Every other double from highest to lowest:
4.1
2.3
1.7

linq55: ToList

//c#
public void Linq55() 
{ 
    string[] words = { "cherry", "apple", "blueberry" };

    var sortedWords = words.OrderBy(x => x);

    var wordList = sortedWords.ToList();

    Console.WriteLine("The sorted word list:");
    wordList.ForEach(Console.WriteLine);
}

//dart
linq55(){
  var words = [ "cherry", "apple", "blueberry" ]; 
  
  var sortedWords = orderBy(words);
  
  var wordList = sortedWords.toList(); 
  
  print("The sorted word list:"); 
  wordList.forEach(print);
}

Output

The sorted word list:
apple
blueberry
cherry

linq56: ToDictionary

//c#
public void Linq56() 
{ 
    var scoreRecords = new[] 
    { 
        new {Name = "Alice", Score = 50},
        new {Name = "Bob"  , Score = 40},
        new {Name = "Cathy", Score = 45}
    };

    var scoreRecordsDict = scoreRecords.ToDictionary(sr => sr.Name);

    Console.WriteLine("Bob's score: {0}", scoreRecordsDict["Bob"]);
}

//dart
linq56(){
  var scoreRecords = [{ 'Name': "Alice", 'Score': 50}, 
                      { 'Name': "Bob"  , 'Score': 40}, 
                      { 'Name': "Cathy", 'Score': 45}];
  
  var scoreRecordsDict = toMap(scoreRecords, (sr) => sr['Name']); 
  
  print("Bob's score: ${scoreRecordsDict['Bob']}"); 
}

Output

Bob's score: {Name: Bob, Score: 40}

linq57: OfType

//c#
public void Linq57() 
{ 
    object[] numbers = { null, 1.0, "two", 3, "four", 5, "six", 7.0 };

    var doubles = numbers.OfType<double>();

    Console.WriteLine("Numbers stored as doubles:");
    doubles.ForEach(Console.WriteLine);
}

//dart
linq57(){
  var numbers = [ null, 1.0, "two", 3, "four", 5, "six", 7.0 ]; 
  
  var doubles = ofType(numbers, double); 
  
  print("Numbers stored as doubles:"); 
  doubles.forEach(print);
}

Output

Numbers stored as doubles:
1.0
7.0

LINQ - Element Operators

linq58: First - Simple

//c#
public void Linq58() 
{ 
    var products = GetProductList();

    var product12 = products
        .Where(p => p.ProductID == 12)
        .First();

    ObjectDumper.Write(product12);
}

//dart
linq58(){
  var products = productsList(); 
  
  var product12 = products 
    .where((p) => p.productId == 12)
    .first; 
  
  print(product12); 
}

Output

{productId: 12, productName: Queso Manchego La Pastora, category: Dairy Products, unitPrice: 38.0, unitsInStock: 86}

linq59: First - Condition

//c#
public void Linq59() 
{ 
    var strings = new []{ "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" };

    var startsWithO = strings.First(s => s.StartsWith('o'));

    Console.WriteLine("A string starting with 'o': {0}", startsWithO);
}

//dart
linq59(){
  var strings = [ "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" ]; 
  
  var startsWithO = strings.firstWhere((s) => s[0] == 'o'); 
  
  print("A string starting with 'o': $startsWithO"); 
}

Output

A string starting with 'o': one

linq61: FirstOrDefault - Simple

//c#
public void Linq61() 
{ 
    var numbers = new int[0];

    var firstNumOrDefault = numbers.FirstOrDefault();

    Console.WriteLine(firstNumOrDefault);
}

//dart
linq61(){
  var numbers = []; 
  
  int firstNumOrDefault = numbers.firstWhere((x) => true, orElse:() => 0); 
  
  print(firstNumOrDefault); 
}

Output

0

linq62: FirstOrDefault - Condition

//c#
public void Linq62() 
{ 
    var products = GetProductList();

    var product789 = products.FirstOrDefault(p => p.ProductID == 789);

    Console.WriteLine("Product 789 exists: {0}", product789 != null);
}

//dart
linq62(){
  var products = productsList(); 
  
  var product789 = products.firstWhere((p) => p.productId == 789, orElse:() => null); 
  
  print("Product 789 exists: ${product789 != null}"); 
}

Output

Product 789 exists: false

linq64: ElementAt

//c#
public void Linq64() 
{ 
    var numbers = new [] { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

    var fourthLowNum = numbers
        .Where(num => num > 5)
        .ElementAt(1);

    Console.WriteLine("Second number > 5: {0}", fourthLowNum);
}

//dart
linq64(){
  var numbers = [ 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 ]; 
  
  int fourthLowNum = numbers 
    .where((n) => n > 5)
    .elementAt(1); 
  
  print("Second number > 5: $fourthLowNum"); 
}

Output

Second number > 5: 8

LINQ - Generation Operators

Dart utils added

List range(int from, [int to]) =>
  to != null 
    ? new List.generate(to, (x) => x + from)
    : new List.generate(from, (x) => x);

linq65: Range

//c#
public void Linq65() 
{ 
    var numbers = Enumerable.Range(100, 50)
        .Select(n => new { Number = n, OddEven = n % 2 == 1 ? "odd" : "even" });

    numbers.ForEach((n) => Console.WriteLine("The number {0} is {1}.", n.Number, n.OddEven));

}

//dart
linq65(){
  var numbers = range(100, 50)
    .map((n) => { 'Number': n, 'OddEven': n % 2 == 1 ? "odd" : "even" }); 
      
  numbers.forEach((n) =>
    print("The number ${n['Number']} is ${n['OddEven']}.")); 
}

Output

The number 100 is even.
The number 101 is odd.
The number 102 is even.
The number 103 is odd.
The number 104 is even.
The number 105 is odd.
The number 106 is even.
The number 107 is odd.
The number 108 is even.
The number 109 is odd.
The number 110 is even.
...

linq66: Repeat

//c#
public void Linq66() 
{ 
    var numbers = Enumerable.Repeat(7, 10);

    numbers.ForEach(Console.WriteLine);
}

//dart
linq66(){
  var numbers = new List.filled(10, 7); 

  numbers.forEach(print);
}

Output

7
7
7
7
7
7
7
7
7
7

LINQ - Quantifiers

linq67: Any - Simple

//c#
public void Linq67() 
{ 
    var words = new []{ "believe", "relief", "receipt", "field" };

    var iAfterE = words.Any(w => w.Contains("ei"));

    Console.WriteLine($"There is a word in the list that contains 'ei': {iAfterE}");
}

//dart
linq67(){
  var words = [ "believe", "relief", "receipt", "field" ]; 
  
  bool iAfterE = words.any((w) => w.contains("ei")); 
  
  print("There is a word that contains in the list that contains 'ei': $iAfterE"); 
}

Output

There is a word that contains in the list that contains 'ei': true

linq69: Any - Grouped

//c#
public void Linq69() 
{ 
    var products = GetProductList();

    var productGroups = products
        .GroupBy(prod => prod.Category)
        .Where(prodGroup => prodGroup.Any(p => p.UnitsInStock == 0))
        .Select(prodGroup => new { Category = prodGroup.Key, Products = prodGroup });

    ObjectDumper.Write(productGroups, 1);
}

//dart
linq69(){
  var products = productsList(); 
  var productGroups = group(products, by:(p) => p.category)
    .where((g) => g.values.any((p) => p.unitsInStock == 0))
    .map((g) => { 'Category': g.key, 'Products': g });

   productGroups.forEach(print);
}

Output

{Category: Condiments, Products: {{productId: 3, productName: Aniseed Syrup, category: Condiments, unitPrice: 10.0, unitsInStock: 13}, {productId: 4, productName: Chef Anton's Cajun Seasoning, category: Condiments, unitPrice: 22.0, unitsInStock: 53}, {productId: 5, productName: Chef Anton's Gumbo Mix, category: Condiments, unitPrice: 21.35, unitsInStock: 0}, {productId: 6, productName: Grandma's Boysenberry Spread, category: Condiments, unitPrice: 25.0, unitsInStock: 120}, {productId: 8, productName: Northwoods Cranberry Sauce, category: Condiments, unitPrice: 40.0, unitsInStock: 6}, {productId: 15, productName: Genen Shouyu, category: Condiments, unitPrice: 15.5, unitsInStock: 39}, {productId: 44, productName: Gula Malacca, category: Condiments, unitPrice: 19.45, unitsInStock: 27}, {productId: 61, productName: Sirop d'�rable, category: Condiments, unitPrice: 28.5, unitsInStock: 113}, {productId: 63, productName: Vegie-spread, category: Condiments, unitPrice: 43.9, unitsInStock: 24}, {productId: 65, productName: Louisiana Fiery Hot Pepper Sauce, category: Condiments, unitPrice: 21.05, unitsInStock: 76}, {productId: 66, productName: Louisiana Hot Spiced Okra, category: Condiments, unitPrice: 17.0, unitsInStock: 4}, {productId: 77, productName: Original Frankfurter gr�ne So�e, category: Condiments, unitPrice: 13.0, unitsInStock: 32}}}
...

linq70: All - Simple

//c#
public void Linq70() 
{  
    var numbers = new [] { 1, 11, 3, 19, 41, 65, 19 };

    var onlyOdd = numbers.All(n => n % 2 == 1);

    Console.WriteLine($"The list contains only odd numbers: {onlyOdd}");
}

//dart
linq70(){
  var numbers = [ 1, 11, 3, 19, 41, 65, 19 ]; 
  
  bool onlyOdd = numbers.every((n) => n % 2 == 1); 
  
  print("The list contains only odd numbers: $onlyOdd"); 
}

Output

The list contains only odd numbers: true

linq72: All - Grouped

//c#
public void Linq72() 
{ 
    var products = GetProductList();

    var productGroups = products
        .GroupBy(prod => prod.Category)
        .Where(prodGroup => prodGroup.All(p => p.UnitsInStock > 0))
        .Select(prodGroup => new { Category = prodGroup.Key, Products = prodGroup });

    ObjectDumper.Write(productGroups, 1);
}

//dart
linq72(){
  var products = productsList(); 
  
  var productGroups = group(products, by:(p) => p.category)
    .where((g) => g.values.every((p) => p.unitsInStock > 0))
    .map((g) => { 'Category': g.key, 'Products': g });
      
  productGroups.forEach(print);
}

Output

{Category: Grains/Cereals, Products: {{productId: 22, productName: Gustaf's Kn�ckebr�d, category: Grains/Cereals, unitPrice: 21.0, unitsInStock: 104}, {productId: 23, productName: Tunnbr�d, category: Grains/Cereals, unitPrice: 9.0, unitsInStock: 61}, {productId: 42, productName: Singaporean Hokkien Fried Mee, category: Grains/Cereals, unitPrice: 14.0, unitsInStock: 26}, {productId: 52, productName: Filo Mix, category: Grains/Cereals, unitPrice: 7.0, unitsInStock: 38}, {productId: 56, productName: Gnocchi di nonna Alice, category: Grains/Cereals, unitPrice: 38.0, unitsInStock: 21}, {productId: 57, productName: Ravioli Angelo, category: Grains/Cereals, unitPrice: 19.5, unitsInStock: 36}, {productId: 64, productName: Wimmers gute Semmelkn�del, category: Grains/Cereals, unitPrice: 33.25, unitsInStock: 22}}}
...

LINQ - Aggregate Operators

Dart utils added

sum(Iterable seq, [fn(x)]) =>
  seq.fold(0, (prev, element) => prev + (fn != null ? fn(element) : element));

min(Iterable seq) =>
  seq.fold(double.MAX_FINITE, (prev, element) => prev.compareTo(element) > 0 ? element : prev);

max(Iterable seq) =>
  seq.fold(double.MIN_POSITIVE, (prev, element) => prev.compareTo(element) > 0 ? prev : element);

avg(Iterable seq) => sum(seq) / seq.length;

linq73: Count - Simple

//c#
public void Linq73() 
{ 
    var primeFactorsOf300 = new [] { 2, 2, 3, 5, 5 };

    var uniqueFactors = primeFactorsOf300.Distinct().Count();

    Console.WriteLine($"There are {uniqueFactors} unique prime factors of 300.");
}

//dart
linq73(){
  var factorsOf300 = [ 2, 2, 3, 5, 5 ]; 
  
  int uniqueFactors = factorsOf300.toSet().length; 
  
  print("There are $uniqueFactors unique factors of 300."); 
}

Output

There are 3 unique factors of 300.

linq74: Count - Conditional

//c#
public void Linq74() 
{ 
    var numbers = new [] { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

    var oddNumbers = numbers.Count(n => n % 2 == 1);

    Console.WriteLine($"There are {oddNumbers} odd numbers in the list.");
}

//dart
linq74(){
  var numbers = [ 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 ]; 
  
  int oddNumbers = numbers.where((n) => n % 2 == 1).length; 
  
  print("There are $oddNumbers odd numbers in the list."); 
}

Output

There are 5 odd numbers in the list.

linq76: Count - Nested

//c#
public void Linq76() 
{ 
    var customers = GetCustomerList();

    var orderCounts = customers
        .Select(cust => new { cust.CustomerID, OrderCount = cust.Orders.Count() });

    ObjectDumper.Write(orderCounts);
}

//dart
linq76(){
  var customers = customersList(); 
  
  var orderCounts = customers
    .map((c) => { 'CustomerId': c.customerId, 'OrderCount': c.orders.length }); 

  orderCounts.forEach(print);
}

Output

{CustomerId: ALFKI, OrderCount: 6}
{CustomerId: ANATR, OrderCount: 4}
{CustomerId: ANTON, OrderCount: 7}
{CustomerId: AROUT, OrderCount: 13}
{CustomerId: BERGS, OrderCount: 18}
{CustomerId: BLAUS, OrderCount: 7}
{CustomerId: BLONP, OrderCount: 11}
...

linq77: Count - Grouped

//c#
public void Linq77() 
{ 
    var products = GetProductList();

    var categoryCounts = products
        .GroupBy(prod => prod.Category)
        .Select(prodGroup => new { Category = prodGroup.Key, ProductCount = prodGroup.Count() });

    ObjectDumper.Write(categoryCounts);
}

//dart
linq77(){
  var products = productsList(); 
  
  var categoryCounts = group(products, by:(p) => p.category)
    .map((g) => { 'Category': g.key, 'ProductCount': g.length });      

  categoryCounts.forEach(print);
}

Output

{Category: Dairy Products, ProductCount: 10}
{Category: Grains/Cereals, ProductCount: 7}
{Category: Confections, ProductCount: 13}
{Category: Seafood, ProductCount: 12}
{Category: Condiments, ProductCount: 12}
{Category: Meat/Poultry, ProductCount: 6}
{Category: Produce, ProductCount: 5}
{Category: Beverages, ProductCount: 12}

linq78: Sum - Simple

//c#
public void Linq78() 
{ 
    var numbers = new [] { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

    var numSum = numbers.Sum();

    Console.WriteLine($"The sum of the numbers is {numSum}.");
}

//dart
linq78(){
  var numbers = [ 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 ]; 
  
  var numSum = sum(numbers); 
  
  print("The sum of the numbers is $numSum."); 
}

Output

The sum of the numbers is 45.

linq79: Sum - Projection

//c#
public void Linq79() 
{ 
    var  words = new [] { "cherry", "apple", "blueberry" };

    var totalChars = words.Sum(w => w.Length);

    Console.WriteLine($"There are a total of {totalChars} characters in these words.");
}

//dart
linq79(){
  var words = [ "cherry", "apple", "blueberry" ]; 
  
  var totalChars = sum(words, (w) => w.length); 
  
  print("There are a total of $totalChars characters in these words.");
}

Output

There are a total of 20 characters in these words.

linq80: Sum - Grouped

//c#
public void Linq80() 
{ 
    var products = GetProductList();

    var categories = products
        .GroupBy(prod => prod.Category)
        .Select(prodGroup => new { Category = prodGroup.Key, TotalUnitsInStock = prodGroup.Sum(p => p.UnitsInStock) });

    ObjectDumper.Write(categories);
}

//dart
linq80(){
  var products = productsList(); 
  
  var categories = group(products, by:(p) => p.category)
    .map((g) => { 'Category': g.key, 'TotalUnitsInStock': sum(g.values, (p) => p.unitsInStock) }); 
      
  categories.forEach(print);
}

Output

{Category: Dairy Products, TotalUnitsInStock: 393}
{Category: Grains/Cereals, TotalUnitsInStock: 308}
{Category: Confections, TotalUnitsInStock: 386}
{Category: Seafood, TotalUnitsInStock: 701}
{Category: Condiments, TotalUnitsInStock: 507}
{Category: Meat/Poultry, TotalUnitsInStock: 165}
{Category: Produce, TotalUnitsInStock: 100}
{Category: Beverages, TotalUnitsInStock: 559}

linq81: Min - Simple

//c#
public void Linq81() 
{ 
    var numbers = new []{ 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

    var minNum = numbers.Min();

    Console.WriteLine($"The minimum number is {minNum}.");
}

//dart
linq81(){
  var numbers = [ 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 ]; 
  
  int minNum = min(numbers); 
  
  print("The minimum number is $minNum.");
}

Output

The minimum number is 0.

linq82: Min - Projection

//c#
public void Linq82() 
{ 
    var words = new [] { "cherry", "apple", "blueberry" };

    var shortestWord = words.Min(w => w.Length);

    Console.WriteLine($"The shortest word is {shortestWord} characters long.");
}

//dart
linq82(){
  var words = [ "cherry", "apple", "blueberry" ]; 
  
  var shortestWord = min(words.map((x) => x.length));
  
  print("The shortest word is $shortestWord characters long."); 
}

Output

The shortest word is 5 characters long.

linq83: Min - Grouped

//c#
public void Linq83() 
{ 
    var products = GetProductList();

    var categories = products
        .GroupBy(prod => prod.Category)
        .Select(prodGroup => new { Category = prodGroup.Key, CheapestPrice = prodGroup.Min(p => p.UnitPrice) });

    ObjectDumper.Write(categories);
}

//dart
linq83(){
  var products = productsList(); 
  
  var categories = group(products, by:(p) => p.category)
    .map((g) => { 'Category': g.key, 'CheapestPrice': min(g.values.map((p) => p.unitPrice)) });

  categories.forEach(print);
}

Output

{Category: Dairy Products, CheapestPrice: 2.5}
{Category: Grains/Cereals, CheapestPrice: 7.0}
{Category: Confections, CheapestPrice: 9.2}
{Category: Seafood, CheapestPrice: 6.0}
{Category: Condiments, CheapestPrice: 10.0}
{Category: Meat/Poultry, CheapestPrice: 7.45}
{Category: Produce, CheapestPrice: 10.0}
{Category: Beverages, CheapestPrice: 4.5}

linq84: Min - Elements

//c#
public void Linq84() 
{ 
    var products = GetProductList();

    var categories = products.GroupBy(prod => prod.Category)
        .Select(prodGroup => new {prodGroup, minPrice = prodGroup.Min(p => p.UnitPrice)})
        .Select(x => new
        {
            Category = x.prodGroup.Key,
            CheapestProducts = x.prodGroup.Where(p => p.UnitPrice == x.minPrice)
        });

    ObjectDumper.Write(categories, 1);
}

//dart
linq84(){
  var products = productsList(); 
  
  var categories = group(products, by:(p) => p.category)
    .map((g){
      var minPrice = min(g.values.map((p) => p.unitPrice));
      return { 'Category': g.key, 'CheapestProducts': g.values.where((p) => p.unitPrice == minPrice) };
    });

  categories.forEach(print);
}

Output

{Category: Dairy Products, CheapestProducts: {{productId: 33, productName: Geitost, category: Dairy Products, unitPrice: 2.5, unitsInStock: 112}}}
{Category: Grains/Cereals, CheapestProducts: {{productId: 52, productName: Filo Mix, category: Grains/Cereals, unitPrice: 7.0, unitsInStock: 38}}}
{Category: Confections, CheapestProducts: {{productId: 19, productName: Teatime Chocolate Biscuits, category: Confections, unitPrice: 9.2, unitsInStock: 25}}}
{Category: Seafood, CheapestProducts: {{productId: 13, productName: Konbu, category: Seafood, unitPrice: 6.0, unitsInStock: 24}}}
{Category: Condiments, CheapestProducts: {{productId: 3, productName: Aniseed Syrup, category: Condiments, unitPrice: 10.0, unitsInStock: 13}}}
{Category: Meat/Poultry, CheapestProducts: {{productId: 54, productName: Tourti�re, category: Meat/Poultry, unitPrice: 7.45, unitsInStock: 21}}}
{Category: Produce, CheapestProducts: {{productId: 74, productName: Longlife Tofu, category: Produce, unitPrice: 10.0, unitsInStock: 4}}}
{Category: Beverages, CheapestProducts: {{productId: 24, productName: Guaran� Fant�stica, category: Beverages, unitPrice: 4.5, unitsInStock: 20}}}

linq85: Max - Simple

//c#
public void Linq85() 
{ 
    var numbers = new []{ 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

    var maxNum = numbers.Max();

    Console.WriteLine($"The maximum number is {maxNum}.");
}

//dart
linq85(){
  var numbers = [ 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 ]; 
  
  var maxNum = max(numbers); 
  
  print("The maximum number is $maxNum."); 
}

Output

The maximum number is 9.

linq86: Max - Projection

//c#
public void Linq86() 
{ 
    var words = new [] { "cherry", "apple", "blueberry" };

    var longestLength = words.Max(w => w.Length);

    Console.WriteLine($"The longest word is {longestLength} characters long.");}

//dart
linq86(){
  var words = [ "cherry", "apple", "blueberry" ]; 
  
  int longestLength = max(words.map((w) => w.length)); 
  
  print("The longest word is $longestLength characters long."); 
}

Output

The longest word is 9 characters long.

linq87: Max - Grouped

//c#
public void Linq87() 
{ 
    var products = GetProductList();

    var categories = products
        .GroupBy(prod => prod.Category)
        .Select(prodGroup => new { Category = prodGroup.Key, MostExpensivePrice = prodGroup.Max(p => p.UnitPrice) });

    ObjectDumper.Write(categories);
}

//dart
linq87(){
  var products = productsList(); 
  
  var categories = group(products, by:(p) => p.category)
    .map((g) => { 'Category': g.key, 'MostExpensivePrice': max(g.values.map((p) => p.unitPrice)) });      

  categories.forEach(print);
}

Output

{Category: Dairy Products, MostExpensivePrice: 55.0}
{Category: Grains/Cereals, MostExpensivePrice: 38.0}
{Category: Confections, MostExpensivePrice: 81.0}
{Category: Seafood, MostExpensivePrice: 62.5}
{Category: Condiments, MostExpensivePrice: 43.9}
{Category: Meat/Poultry, MostExpensivePrice: 123.79}
{Category: Produce, MostExpensivePrice: 53.0}
{Category: Beverages, MostExpensivePrice: 263.5}

linq88: Max - Elements

//c#
public void Linq88() 
{ 
    var products = GetProductList();

    var categories = products.GroupBy(prod => prod.Category)
        .Select(prodGroup => new {prodGroup, maxPrice = prodGroup.Max(p => p.UnitPrice)})
        .Select(x => new
        {
            Category = x.prodGroup.Key,
            MostExpensiveProducts = x.prodGroup.Where(p => p.UnitPrice == x.maxPrice)
        });

    ObjectDumper.Write(categories, 1);
}

//dart
linq88(){
  var products = productsList(); 
  
  var categories = group(products, by:(p) => p.category)
    .map((g){
      var maxPrice = max(g.values.map((p) => p.unitPrice));
      return { 'Category': g.key, 'MostExpensiveProducts': g.values.where((p) => p.unitPrice == maxPrice) };
    });

  categories.forEach(print);
}

Output

{Category: Dairy Products, MostExpensiveProducts: {{productId: 59, productName: Raclette Courdavault, category: Dairy Products, unitPrice: 55.0, unitsInStock: 79}}}
{Category: Grains/Cereals, MostExpensiveProducts: {{productId: 56, productName: Gnocchi di nonna Alice, category: Grains/Cereals, unitPrice: 38.0, unitsInStock: 21}}}
{Category: Confections, MostExpensiveProducts: {{productId: 20, productName: Sir Rodney's Marmalade, category: Confections, unitPrice: 81.0, unitsInStock: 40}}}
{Category: Seafood, MostExpensiveProducts: {{productId: 18, productName: Carnarvon Tigers, category: Seafood, unitPrice: 62.5, unitsInStock: 42}}}
{Category: Condiments, MostExpensiveProducts: {{productId: 63, productName: Vegie-spread, category: Condiments, unitPrice: 43.9, unitsInStock: 24}}}
{Category: Meat/Poultry, MostExpensiveProducts: {{productId: 29, productName: Th�ringer Rostbratwurst, category: Meat/Poultry, unitPrice: 123.79, unitsInStock: 0}}}
{Category: Produce, MostExpensiveProducts: {{productId: 51, productName: Manjimup Dried Apples, category: Produce, unitPrice: 53.0, unitsInStock: 20}}}
{Category: Beverages, MostExpensiveProducts: {{productId: 38, productName: C�te de Blaye, category: Beverages, unitPrice: 263.5, unitsInStock: 17}}}

linq89: Average - Simple

//c#
public void Linq89() 
{ 
    var numbers = new [] { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

    var averageNum = numbers.Average();

    Console.WriteLine($"The average number is {averageNum}.");
}

//dart
linq89(){
  var numbers = [ 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 ]; 
  
  var averageNum = avg(numbers); 
  
  print("The average number is $averageNum.");
}

Output

The average number is 4.5.

linq90: Average - Projection

//c#
public void Linq90() 
{ 
    var words = new [] { "cherry", "apple", "blueberry" };

    var averageLength = words.Average(w => w.Length);

    Console.WriteLine($"The average word length is {averageLength} characters.");
}

//dart
linq90(){
  var words = [ "cherry", "apple", "blueberry" ]; 
  
  var averageLength = avg(words.map((w) => w.length)); 
  
  print("The average word length is $averageLength characters."); 
}

Output

The average word length is 6.666666666666667 characters.

linq91: Average - Grouped

//c#
public void Linq91() 
{ 
    var  products = GetProductList();

    var categories = products
        .GroupBy(prod => prod.Category)
        .Select(prodGroup => new { Category = prodGroup.Key, AveragePrice = prodGroup.Average(p => p.UnitPrice) });

    ObjectDumper.Write(categories);
}

//dart
linq91(){
  var products = productsList(); 
  
  var categories = group(products, by:(p) => p.category)
    .map((g) => { 'Category': g.key, 'AveragePrice': avg(g.values.map((p) => p.unitPrice)) });

  categories.forEach(print);
}

Output

{Category: Dairy Products, AveragePrice: 28.73}
{Category: Grains/Cereals, AveragePrice: 20.25}
{Category: Confections, AveragePrice: 25.16}
{Category: Seafood, AveragePrice: 20.6825}
{Category: Condiments, AveragePrice: 23.0625}
{Category: Meat/Poultry, AveragePrice: 54.00666666666667}
{Category: Produce, AveragePrice: 32.37}
{Category: Beverages, AveragePrice: 37.979166666666664}

linq92: Aggregate - Simple

//c#
public void Linq92() 
{ 
    var doubles = new [] { 1.7, 2.3, 1.9, 4.1, 2.9 };

    var product = doubles.Aggregate((runningProduct, nextFactor) => runningProduct * nextFactor);

    Console.WriteLine($"Total product of all numbers: {product}");
}

//dart
linq92(){
  var doubles = [ 1.7, 2.3, 1.9, 4.1, 2.9 ]; 
  
  var product = doubles.reduce((runningProduct, nextFactor) => runningProduct * nextFactor); 
  
  print("Total product of all numbers: $product");
}

Output

Total product of all numbers: 88.33080999999999

linq93: Aggregate - Seed

//c#
public void Linq93() 
{ 
    var startBalance = 100.0;

    var attemptedWithdrawals = new []{ 20, 10, 40, 50, 10, 70, 30 };

    var endBalance = attemptedWithdrawals
        .Aggregate(startBalance, 
                    (balance, nextWithdrawal) =>
                    ((nextWithdrawal <= balance) ? (balance - nextWithdrawal) : balance));

    Console.WriteLine($"Ending balance: {endBalance}");
}

//dart
linq93(){
  var startBalance = 100.0; 
  
  var attemptedWithdrawals = [ 20, 10, 40, 50, 10, 70, 30 ]; 
  
  var endBalance = attemptedWithdrawals.fold(startBalance, 
    (balance, nextWithdrawal) => 
      ((nextWithdrawal <= balance) ? (balance - nextWithdrawal) : balance)); 
  
  print("Ending balance: $endBalance"); 
}

Output

Ending balance: 20.0

LINQ - Miscellaneous Operators

Dart utils added

concat(Iterable seq, Iterable withSeq) =>
  seq.toList()..addAll(withSeq);

bool seqEq(Iterable seq, Iterable withSeq) =>    
  seq.length == withSeq.length 
  && range(seq.length).every((i) => seq.elementAt(i) == withSeq.elementAt(i));

linq94: Concat - 1

//c#
public void Linq94() 
{ 
    int[] numbersA = { 0, 2, 4, 5, 6, 8, 9 };
    int[] numbersB = { 1, 3, 5, 7, 8 };

    var allNumbers = numbersA.Concat(numbersB);

    Console.WriteLine("All numbers from both arrays:");
    allNumbers.ForEach(Console.WriteLine);
}

//dart
linq94(){
  var numbersA = [ 0, 2, 4, 5, 6, 8, 9 ]; 
  var numbersB = [ 1, 3, 5, 7, 8 ]; 
  
  var allNumbers = concat(numbersA, numbersB); 
  
  print("All numbers from both arrays:");
  allNumbers.forEach(print);
}

Output

All numbers from both arrays:
0
2
4
5
6
8
9
1
3
5
7
8

linq95: Concat - 2

//c#
public void Linq95() 
{ 
    var customers = GetCustomerList();
    var products = GetProductList();

    var customerNames = customers
        .Select(cust => cust.CompanyName);
    var productNames = products
        .Select(prod => prod.ProductName);

    var allNames = customerNames.Concat(productNames);

    Console.WriteLine("Customer and product names:");
    allNames.ForEach(Console.WriteLine);
}

//dart
linq95(){
  var customers = customersList(); 
  var products = productsList(); 
  
  var customerNames = customers
    .map((c) => c.companyName);
  var productNames = products
    .map((p) => p.productName);
  
  var allNames = concat(customerNames, productNames); 
  
  print("Customer and product names:");
  allNames.forEach(print);
}

Output

Customer and product names:
Alfreds Futterkiste
Ana Trujillo Emparedados y helados
Antonio Moreno Taquer�a
Around the Horn
Berglunds snabbk�p
Blauer See Delikatessen
...

linq96: EqualAll - 1

//c#
public void Linq96() 
{ 
    var wordsA = new string[] { "cherry", "apple", "blueberry" };
    var wordsB = new string[] { "cherry", "apple", "blueberry" };

    var match = wordsA.SequenceEqual(wordsB);

    Console.WriteLine($"The sequences match: {match}");
}

//dart
linq96(){
  var wordsA = [ "cherry", "apple", "blueberry" ]; 
  var wordsB = [ "cherry", "apple", "blueberry" ]; 
  
  bool match = seqEq(wordsA, wordsB); 
  
  print("The sequences match: $match");
}

Output

The sequences match: true

linq97: EqualAll - 2

//c#
public void Linq97() 
{ 
    var wordsA = new string[] { "cherry", "apple", "blueberry" };
    var wordsB = new string[] { "apple", "blueberry", "cherry" };

    var match = wordsA.SequenceEqual(wordsB);

    Console.WriteLine($"The sequences match: {match}");
}

//dart
linq97(){
  var wordsA = [ "cherry", "apple", "blueberry" ]; 
  var wordsB = [ "apple", "blueberry", "cherry" ]; 
  
  bool match = seqEq(wordsA, wordsB); 
  
  print("The sequences match: $match");
}

Output

The sequences match: false

LINQ - Query Execution

linq99: Deferred Execution

//c#
public void Linq99() 
{ 
    // Queries are not executed until you enumerate over them.
    int[] numbers = new int[] { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

    int i = 0;
    var simpleQuery = numbers
        .Select(x => i++);

    // The local variable 'i' is not incremented until the query is executed in the foreach loop.
    Console.WriteLine($"The current value of i is {i}"); //i is still zero

    simpleQuery.ForEach(item => Console.WriteLine($"v = {item}, i = {i}")); // now i is incremented  
}

//dart
linq99(){
  var numbers = [ 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 ]; 
  
  var i = 0; 
  var q = numbers.map((n) => ++i);
  
  q.forEach((v) => 
    print("v = $v, i = $i"));
}

Output

v = 1, i = 1
v = 2, i = 2
v = 3, i = 3
v = 4, i = 4
v = 5, i = 5
v = 6, i = 6
v = 7, i = 7
v = 8, i = 8
v = 9, i = 9
v = 10, i = 10

linq100: Immediate Execution

//c#
public void Linq100() 
{ 
    // Methods like ToList(), Max(), and Count() cause the query to be executed immediately.            
    int[] numbers = new int[] { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };

    int i = 0;
    var immediateQuery = numbers
        .Select(x =>  ++i)
        .ToList();

    Console.WriteLine("The current value of i is {0}", i); //i has been incremented

    immediateQuery.ForEach(item => Console.WriteLine($"v = {item}, i = {i}"));
} 

//dart
linq100(){
  var numbers = [ 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 ]; 
  
  var i = 0; 
  var q = numbers.map((n) => ++i).toList();
  
  q.forEach((v) => 
    print("v = $v, i = $i"));
}

Output

v = 1, i = 10
v = 2, i = 10
v = 3, i = 10
v = 4, i = 10
v = 5, i = 10
v = 6, i = 10
v = 7, i = 10
v = 8, i = 10
v = 9, i = 10
v = 10, i = 10

linq101: Query Reuse

//c#
public void Linq101() 
{ 
    // Deferred execution lets us define a query once and then reuse it later in various ways.
    int[] numbers = new int[] { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
    var lowNumbers = numbers
        .Where(num => num <= 3);

    Console.WriteLine("First run numbers <= 3:");
    lowNumbers.ForEach(Console.WriteLine);

    // Modify the source data.
    for (int i = 0; i < 10; i++)
    {
        numbers[i] = -numbers[i];
    }

    // During this second run, the same query object,
    // lowNumbers, will be iterating over the new state
    // of numbers[], producing different results:
    Console.WriteLine("Second run numbers <= 3:");
    lowNumbers.ForEach(Console.WriteLine);
} 

//dart
linq101(){
  var numbers = [ 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 ]; 
  var lowNumbers = numbers
    .where((n) => n <= 3); 
  
  print("First run numbers <= 3:");
  lowNumbers.forEach(print);
  
  for (int i = 0; i < 10; i++){ 
    numbers[i] = -numbers[i]; 
  } 
  
  print("Second run numbers <= 3:"); 
  lowNumbers.forEach(print);
}

Output

First run numbers <= 3:
1
3
2
0
Second run numbers <= 3:
-5
-4
-1
-3
-9
-8
-6
-7
-2
0

LINQ - Join Operators

Dart utils added

join(Iterable seq, Iterable withSeq, bool match(x,y)) =>
  seq.expand((x) => withSeq
    .where((y) => match(x,y))
    .map((y) => [x,y]));

joinGroup(Iterable seq, Iterable withSeq, bool match(x,y)) =>
  group(join(seq, withSeq, match), by:(j) => j[0]);  

linq102: Cross Join

//c#
public void Linq102() 
{ 
    var categories = new [] {"Beverages","Condiments","Vegetables","Dairy Products","Seafood" };

    var products = GetProductList();

    var q = categories
        .Join(products, c => c, p => p.Category, 
            (c, p) => new {Category = c, p.ProductName});

    q.ForEach(v => Console.WriteLine($"Category: {v.Category}: Product {v.ProductName}"));
}

//dart
linq102(){
  var categories = [ "Beverages", "Condiments", "Vegetables", "Dairy Products", "Seafood" ];  
  
  var products = productsList(); 
  
  var q = join(categories, products, (c,p) => c == p.category)
    .map((j) => { 'Category': j[0], 'ProductName': j[1].productName });

  q.forEach(print);
}

Output

{Category: Beverages, ProductName: Chai}
{Category: Beverages, ProductName: Chang}
{Category: Beverages, ProductName: Guaran� Fant�stica}
{Category: Beverages, ProductName: Sasquatch Ale}
{Category: Beverages, ProductName: Steeleye Stout}
{Category: Beverages, ProductName: C�te de Blaye}
{Category: Beverages, ProductName: Chartreuse verte}
{Category: Beverages, ProductName: Ipoh Coffee}
...

linq103: Group Join

//c#
public void Linq103() 
{ 
    var categories = new [] {"Beverages","Condiments","Vegetables","Dairy Products","Seafood" };  

    var products = GetProductList(); 

    var q = categories
        .GroupJoin(products, c => c, p => p.Category,
            (c, ps) => new {Category = c, Products = ps}); 

    q.ForEach((v) => 
    {
        Console.WriteLine(v.Category + ":"); 
        v.Products.ForEach(p => Console.WriteLine($"\t{p.ProductName}"));
    });
}

//dart
linq103(){
  var categories = [ "Beverages", "Condiments", "Vegetables", "Dairy Products", "Seafood" ];  
  
  var products = productsList(); 
  
  var q = joinGroup(categories, products, (c,p) => c == p.category)
    .map((j) => { 'Category': j.key, 'Products': j.values.map((g) => g[1]) });

  q.forEach((v){
    print("${v['Category']}:");
    v['Products'].forEach((p) => print("   ${p.productName}"));
  });
}

Output

Dairy Products:
   Queso Cabrales
   Queso Manchego La Pastora
   Gorgonzola Telino
   Mascarpone Fabioli
   Geitost
   Raclette Courdavault
   Camembert Pierrot
   Gudbrandsdalsost
   Flotemysost
   Mozzarella di Giovanni
Condiments:
   Aniseed Syrup
   Chef Anton's Cajun Seasoning
   Chef Anton's Gumbo Mix
   Grandma's Boysenberry Spread
   Northwoods Cranberry Sauce
   Genen Shouyu
   Gula Malacca
   Sirop d'�rable
   Vegie-spread
   Louisiana Fiery Hot Pepper Sauce
   Louisiana Hot Spiced Okra
   Original Frankfurter gr�ne So�e
...

linq104: Cross Join with Group Join

//c#
public void Linq104() 
{ 
    var categories = new [] {"Beverages","Condiments","Vegetables","Dairy Products","Seafood" };  

    var products = GetProductList();

    var prodByCategory = categories
        .GroupJoin(products, cat => cat, prod => prod.Category, 
            (category, prods) => new {category, prods})
        .SelectMany(x => x.prods, (x, plist) => new {Category = x.category, plist.ProductName});

    prodByCategory.ForEach(item => Console.WriteLine($"{item.ProductName }: {item.Category}"));
}

//dart
linq104(){
  var categories = [ "Beverages", "Condiments", "Vegetables", "Dairy Products", "Seafood" ];  
  
  var products = productsList(); 
  
  var q = joinGroup(categories, products, (c,p) => c == p.category)
    .expand((j) => j.values.map((g) => g[1])
      .map((p) => { 'Category': j.key, 'ProductName': p.productName }));

  q.forEach((v) => 
    print("${v['ProductName']}: ${v['Category']}"));
}

Output

Queso Cabrales: Dairy Products
Queso Manchego La Pastora: Dairy Products
Gorgonzola Telino: Dairy Products
Mascarpone Fabioli: Dairy Products
Geitost: Dairy Products
Raclette Courdavault: Dairy Products
Camembert Pierrot: Dairy Products
Gudbrandsdalsost: Dairy Products
Flotemysost: Dairy Products
Mozzarella di Giovanni: Dairy Products
Aniseed Syrup: Condiments
Chef Anton's Cajun Seasoning: Condiments
Chef Anton's Gumbo Mix: Condiments
...

linq105: Left Outer Join

//c#
public void Linq105()  
{ 
    var categories = new [] {"Beverages","Condiments","Vegetables","Dairy Products","Seafood" };  

    var products = GetProductList(); 

    var q = categories
        .GroupJoin(products, cat => cat, prod => prod.Category, 
            (category, prods) => new {category, prods})
        .SelectMany(x => x.prods.DefaultIfEmpty(),
            (x, p) => new {Category = x.category, ProductName = p == null ? "(No products)" : p.ProductName}); 

    q.ForEach(item => Console.WriteLine($"{item.ProductName }: {item.Category}"));
}

//dart
linq105(){
  var categories = [ "Beverages", "Condiments", "Vegetables", "Dairy Products", "Seafood" ];  
  
  var products = productsList(); 
  
  var q = categories
    .expand((c){
      var catProducts = products.where((p) => c == p.category);
      return catProducts.isEmpty 
        ? [{ 'Category': c, 'ProductName': "(No products)" }]
        : catProducts.map((p) => { 'Category': c, 'ProductName': p.productName });
    });

  q.forEach((v) => 
    print("${v['ProductName']}: ${v['Category']}"));
}

Output

Chai: Beverages
Chang: Beverages
Guaran� Fant�stica: Beverages
Sasquatch Ale: Beverages
Steeleye Stout: Beverages
C�te de Blaye: Beverages
Chartreuse verte: Beverages
Ipoh Coffee: Beverages
Laughing Lumberjack Lager: Beverages
Outback Lager: Beverages
Rh�nbr�u Klosterbier: Beverages
Lakkalik��ri: Beverages
Aniseed Syrup: Condiments
Chef Anton's Cajun Seasoning: Condiments
Chef Anton's Gumbo Mix: Condiments
Grandma's Boysenberry Spread: Condiments
Northwoods Cranberry Sauce: Condiments
Genen Shouyu: Condiments
Gula Malacca: Condiments
Sirop d'�rable: Condiments
Vegie-spread: Condiments
Louisiana Fiery Hot Pepper Sauce: Condiments
Louisiana Hot Spiced Okra: Condiments
Original Frankfurter gr�ne So�e: Condiments
(No products): Vegetables
...

Contributors

• mythz (Demis Bellot)