Re-write cascade delete documentation

Fixes #2906 Fixes #828 Fixes #473
dotnet · Jan 9, 2021 · acd93f8 · acd93f8
1 parent ae420d9
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diff --git a/entity-framework/core/saving/cascade-delete.md b/entity-framework/core/saving/cascade-delete.md
diff --git a/samples/core/CascadeDeletes/CascadeDeletes.csproj b/samples/core/CascadeDeletes/CascadeDeletes.csproj
@@ -0,0 +1,15 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+    <PropertyGroup>
+        <OutputType>Exe</OutputType>
+        <TargetFramework>netcoreapp3.1</TargetFramework>
+        <RootNamespace />
+    </PropertyGroup>
+
+    <ItemGroup>
+        <PackageReference Include="Microsoft.EntityFrameworkCore.Design" Version="5.0.1" />
+        <PackageReference Include="Microsoft.EntityFrameworkCore.Sqlite" Version="5.0.1" />
+        <PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="5.0.1" />
+    </ItemGroup>
+
+</Project>
diff --git a/samples/core/CascadeDeletes/IntroOptionalSamples.cs b/samples/core/CascadeDeletes/IntroOptionalSamples.cs
@@ -0,0 +1,171 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Diagnostics;
+
+namespace IntroOptional
+{
+    public static class IntroOptionalSamples
+    {
+        public static void Deleting_principal_parent_1b()
+        {
+            Console.WriteLine($">>>> Sample: {nameof(Deleting_principal_parent_1b)}");
+            Console.WriteLine();
+
+            Helpers.RecreateCleanDatabase();
+            Helpers.PopulateDatabase();
+
+            #region Deleting_principal_parent_1b()
+            using var context = new BlogsContext();
+
+            var blog = context.Blogs.OrderBy(e => e.Name).Include(e => e.Posts).First();
+
+            context.Remove(blog);
+
+            context.SaveChanges();
+            #endregion
+
+            Console.WriteLine();
+        }
+
+        public static void Severing_a_relationship_1b()
+        {
+            Console.WriteLine($">>>> Sample: {nameof(Severing_a_relationship_1b)}");
+            Console.WriteLine();
+
+            Helpers.RecreateCleanDatabase();
+            Helpers.PopulateDatabase();
+
+            #region Severing_a_relationship_1b()
+            using var context = new BlogsContext();
+
+            var blog = context.Blogs.OrderBy(e => e.Name).Include(e => e.Posts).First();
+
+            foreach (var post in blog.Posts)
+            {
+                post.Blog = null;
+            }
+
+            context.SaveChanges();
+            #endregion
+
+            Console.WriteLine();
+        }
+
+        public static void Severing_a_relationship_2b()
+        {
+            Console.WriteLine($">>>> Sample: {nameof(Severing_a_relationship_2b)}");
+            Console.WriteLine();
+
+            Helpers.RecreateCleanDatabase();
+            Helpers.PopulateDatabase();
+
+            #region Severing_a_relationship_1b()
+            using var context = new BlogsContext();
+
+            var blog = context.Blogs.OrderBy(e => e.Name).Include(e => e.Posts).First();
+
+            blog.Posts.Clear();
+
+            context.SaveChanges();
+            #endregion
+
+            Console.WriteLine();
+        }
+    }
+
+    public static class Helpers
+    {
+        public static void RecreateCleanDatabase()
+        {
+            using var context = new BlogsContext(quiet: true);
+
+            context.Database.EnsureDeleted();
+            context.Database.EnsureCreated();
+        }
+
+        public static void PopulateDatabase()
+        {
+            using var context = new BlogsContext(quiet: true);
+
+            context.Add(
+                new Blog
+                {
+                    Name = ".NET Blog",
+                    Posts =
+                    {
+                        new Post
+                        {
+                            Title = "Announcing the Release of EF Core 5.0",
+                            Content = "Announcing the release of EF Core 5.0, a full featured cross-platform..."
+                        },
+                        new Post
+                        {
+                            Title = "Announcing F# 5",
+                            Content = "F# 5 is the latest version of F#, the functional programming language..."
+                        },
+                    }
+                });
+
+            context.SaveChanges();
+        }
+    }
+
+    #region Model
+    public class Blog
+    {
+        public int Id { get; set; }
+
+        public string Name { get; set; }
+
+        public IList<Post> Posts { get; } = new List<Post>();
+    }
+
+    public class Post
+    {
+        public int Id { get; set; }
+
+        public string Title { get; set; }
+        public string Content { get; set; }
+
+        public int? BlogId { get; set; }
+        public Blog Blog { get; set; }
+    }
+    #endregion
+
+    public class BlogsContext : DbContext
+    {
+        private readonly bool _quiet;
+
+        public BlogsContext(bool quiet = false)
+        {
+            _quiet = quiet;
+        }
+
+        public DbSet<Blog> Blogs { get; set; }
+        public DbSet<Post> Posts { get; set; }
+
+        protected override void OnModelCreating(ModelBuilder modelBuilder)
+        {
+            modelBuilder
+                .Entity<Blog>()
+                .HasMany(e => e.Posts)
+                .WithOne(e => e.Blog)
+                .OnDelete(DeleteBehavior.ClientSetNull);
+        }
+
+        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
+        {
+            optionsBuilder
+                .EnableSensitiveDataLogging()
+                .UseSqlServer(@"Server=(localdb)\mssqllocaldb;Database=Scratch;ConnectRetryCount=0");
+            //.UseSqlite("DataSource=test.db");
+
+            if (!_quiet)
+            {
+                optionsBuilder.LogTo(Console.WriteLine, new[] { RelationalEventId.CommandExecuted });
+            }
+        }
+    }
+}
diff --git a/samples/core/CascadeDeletes/IntroRequiredSamples.cs b/samples/core/CascadeDeletes/IntroRequiredSamples.cs
@@ -0,0 +1,188 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Diagnostics;
+
+namespace IntroRequired
+{
+    public static class IntroRequiredSamples
+    {
+        public static void Deleting_principal_parent_1()
+        {
+            Console.WriteLine($">>>> Sample: {nameof(Deleting_principal_parent_1)}");
+            Console.WriteLine();
+
+            Helpers.RecreateCleanDatabase();
+            Helpers.PopulateDatabase();
+
+            #region Deleting_principal_parent_1
+            using var context = new BlogsContext();
+
+            var blog = context.Blogs.OrderBy(e => e.Name).Include(e => e.Posts).First();
+
+            context.Remove(blog);
+
+            context.SaveChanges();
+            #endregion
+
+            Console.WriteLine();
+        }
+
+        public static void Severing_a_relationship_1()
+        {
+            Console.WriteLine($">>>> Sample: {nameof(Severing_a_relationship_1)}");
+            Console.WriteLine();
+
+            Helpers.RecreateCleanDatabase();
+            Helpers.PopulateDatabase();
+
+            #region Severing_a_relationship_1
+            using var context = new BlogsContext();
+
+            var blog = context.Blogs.OrderBy(e => e.Name).Include(e => e.Posts).First();
+
+            foreach (var post in blog.Posts)
+            {
+                post.Blog = null;
+            }
+
+            context.SaveChanges();
+            #endregion
+
+            Console.WriteLine();
+        }
+
+        public static void Severing_a_relationship_2()
+        {
+            Console.WriteLine($">>>> Sample: {nameof(Severing_a_relationship_2)}");
+            Console.WriteLine();
+
+            Helpers.RecreateCleanDatabase();
+            Helpers.PopulateDatabase();
+
+            #region Severing_a_relationship_2
+            using var context = new BlogsContext();
+
+            var blog = context.Blogs.OrderBy(e => e.Name).Include(e => e.Posts).First();
+
+            blog.Posts.Clear();
+
+            context.SaveChanges();
+            #endregion
+
+            Console.WriteLine();
+        }
+
+        public static void Where_cascading_behaviors_happen_1()
+        {
+            Console.WriteLine($">>>> Sample: {nameof(Where_cascading_behaviors_happen_1)}");
+            Console.WriteLine();
+
+            Helpers.RecreateCleanDatabase();
+            Helpers.PopulateDatabase();
+
+            #region Where_cascading_behaviors_happen_1
+            using var context = new BlogsContext();
+
+            var blog = context.Blogs.OrderBy(e => e.Name).First();
+
+            context.Remove(blog);
+
+            context.SaveChanges();
+            #endregion
+
+            Console.WriteLine();
+        }
+    }
+
+    public static class Helpers
+    {
+        public static void RecreateCleanDatabase()
+        {
+            using var context = new BlogsContext(quiet: true);
+
+            context.Database.EnsureDeleted();
+            context.Database.EnsureCreated();
+        }
+
+        public static void PopulateDatabase()
+        {
+            using var context = new BlogsContext(quiet: true);
+
+            context.Add(
+                new Blog
+                {
+                    Name = ".NET Blog",
+                    Posts =
+                    {
+                        new Post
+                        {
+                            Title = "Announcing the Release of EF Core 5.0",
+                            Content = "Announcing the release of EF Core 5.0, a full featured cross-platform..."
+                        },
+                        new Post
+                        {
+                            Title = "Announcing F# 5",
+                            Content = "F# 5 is the latest version of F#, the functional programming language..."
+                        },
+                    }
+                });
+
+            context.SaveChanges();
+        }
+    }
+
+    #region Model
+    public class Blog
+    {
+        public int Id { get; set; }
+
+        public string Name { get; set; }
+
+        public IList<Post> Posts { get; } = new List<Post>();
+    }
+
+    public class Post
+    {
+        public int Id { get; set; }
+
+        public string Title { get; set; }
+        public string Content { get; set; }
+
+        public int BlogId { get; set; }
+        public Blog Blog { get; set; }
+    }
+    #endregion
+
+    public class BlogsContext : DbContext
+    {
+        private readonly bool _quiet;
+
+        public BlogsContext(bool quiet = false)
+        {
+            _quiet = quiet;
+        }
+
+        public DbSet<Blog> Blogs { get; set; }
+        public DbSet<Post> Posts { get; set; }
+
+        protected override void OnModelCreating(ModelBuilder modelBuilder)
+        {
+            modelBuilder.Entity<Blog>().HasMany(e => e.Posts).WithOne(e => e.Blog); //.OnDelete(DeleteBehavior.ClientSetNull);
+        }
+
+        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
+        {
+            optionsBuilder
+                .EnableSensitiveDataLogging()
+                .UseSqlServer(@"Server=(localdb)\mssqllocaldb;Database=Scratch;ConnectRetryCount=0");
+            //.UseSqlite("DataSource=test.db");
+
+            if (!_quiet)
+            {
+                optionsBuilder.LogTo(Console.WriteLine, new[] { RelationalEventId.CommandExecuted });
+            }
+        }
+    }
+}