Mapster - The Mapper of Your Domain

Writing mapping methods is a machine job. Do not waste your time, let Mapster do it.

Installation

Install Mapster with the NuGet CLI:

Install-Package Mapster

Or use the .NET core CLI to install Mapster:

dotnet add package Mapster

Basic usage

Mapping to a new object

Mapster creates the destination object and maps values to it.

var destObject = sourceObject.Adapt<Destination>();

Mapping to an existing object

You create the object, Mapster maps to the object.

sourceObject.Adapt(destObject);

You can get IMapper instance via dependency injection so you do not have to change code when migrating to mapster from automapper

Add Mapster to service collection

services.AddMapster();

And use it with DI

public class Test
{
    public Test(IMapper mapper)
    {
        var sourceObject = mapper.Adapt<Destination>();
    }
}

Queryable Extensions

Mapster also provides extensions to map queryables.

using (MyDbContext context = new MyDbContext())
{
    // Build a Select Expression from DTO
    var destinations = context.Sources.ProjectToType<Destination>().ToList();

    // Versus creating by hand:
    var destinations = context.Sources.Select(c => new Destination {
        Id = c.Id,
        Name = c.Name,
        Surname = c.Surname,
        ....
    })
    .ToList();
}

Generating models & mappers

No need to write your own DTO classes. Mapster provides Mapster.Tool to help you generating models. And if you would like to have explicit mapping, Mapster also generates mapper class for you.

[AdaptTo("[name]Dto"), GenerateMapper]
public class Student {
    ...
}

Then Mapster will generate:

public class StudentDto {
    ...
}
public static class StudentMapper {
    public static StudentDto AdaptToDto(this Student poco) { ... }
    public static StudentDto AdaptTo(this Student poco, StudentDto dto) { ... }
    public static Expression<Func<Student, StudentDto>> ProjectToDto => ...
}

What's new

• Fluent API for code generation
• Automatically generate mapping code on build
• Define setting to nested mapping
• ISet, IDictionary, IReadOnlyDictionary support
• EmptyCollectionIfNull, CreateNewIfNull DestinationTransform
• Several fixes
• New plugins
  • Immutable collection support

Why Mapster?

Performance & Memory efficient

Mapster was designed to be efficient on both speed and memory. You could gain a 4x performance improvement whilst using only 1/3 of memory. And you could gain up to 12x faster performance with

• Roslyn Compiler
• FEC
• Code generation

Method	Mean	StdDev	Error	Gen 0	Gen 1	Gen 2	Allocated
'Mapster 6.0.0'	108.59 ms	1.198 ms	1.811 ms	31000.0000	-	-	124.36 MB
'Mapster 6.0.0 (Roslyn)'	38.45 ms	0.494 ms	0.830 ms	31142.8571	-	-	124.36 MB
'Mapster 6.0.0 (FEC)'	37.03 ms	0.281 ms	0.472 ms	29642.8571	-	-	118.26 MB
'Mapster 6.0.0 (Codegen)'	34.16 ms	0.209 ms	0.316 ms	31133.3333	-	-	124.36 MB
'ExpressMapper 1.9.1'	205.78 ms	5.357 ms	8.098 ms	59000.0000	-	-	236.51 MB
'AutoMapper 10.0.0'	420.97 ms	23.266 ms	35.174 ms	87000.0000	-	-	350.95 MB

Step into debugging

Step-into debugging lets you debug your mapping and inspect values just like your code.

Code Generation

Code generation allows you to

• Validate mapping at compile time
• Getting raw performance
• Seeing your mapping code & debugging
• Finding usage of your models' properties

There are currently two tools which you can choose based on your preferences.

• Mapster.Tool NEW!
• TextTemplate

Change logs

https://github.com/MapsterMapper/Mapster/releases

Usages

• English
• 中文文档 (sp thx to @staneee)

Acknowledgements

JetBrains kindly provides Mapster with a free open-source licence for their Resharper and Rider.

• Resharper makes Visual Studio a much better IDE
• Rider is fast & powerful cross platform .NET IDE