Attribute for configuring DeleteBehavior

Fixes #9621

Added:
DeleteBehaviorAttribute - Stores DeleteBehavior set on the property.
DeleteBehaviorAttributeConvention - Triggers on ForeignKeyAdded, checks if its navigation has DeleteBehavior. If so then sets DeleteBehavior of this foreign key.

Moved:
DeleteBehavior => EFCore.Abstractions and added TypeForward in EFCore

src/EFCore/DeleteBehavior.cs → src/EFCore.Abstractions/DeleteBehavior.cs

@@ -10,12 +10,12 @@ namespace Microsoft.EntityFrameworkCore;
 /// <remarks>
 ///     <para>
 ///         Behaviors in the database are dependent on the database schema being created
-///         appropriately. Using Entity Framework Migrations or <see cref="DatabaseFacade.EnsureCreated" />
-///         will create the appropriate schema.
+///         appropriately. Using Entity Framework Migrations or
+///         <c>EnsureCreated()</c> will create the appropriate schema.
 ///     </para>
 ///     <para>
 ///         Note that the in-memory behavior for entities that are currently tracked by
-///         the <see cref="DbContext" /> can be different from the behavior that happens in the database.
+///         the context can be different from the behavior that happens in the database.
 ///     </para>
 ///     <para>
 ///         See <see href="https://aka.ms/efcore-docs-cascading">Cascade delete and deleting orphans in EF Core</see> for more information and
@@ -25,16 +25,17 @@ namespace Microsoft.EntityFrameworkCore;
 public enum DeleteBehavior
 {
     /// <summary>
-    ///     For entities being tracked by the <see cref="DbContext" />, the values of foreign key properties in
+    ///     For entities being tracked by the context, the values of foreign key properties in
     ///     dependent entities are set to null when the related principal is deleted.
     ///     This helps keep the graph of entities in a consistent state while they are being tracked, such that a
     ///     fully consistent graph can then be written to the database. If a property cannot be set to null because
-    ///     it is not a nullable type, then an exception will be thrown when <see cref="DbContext.SaveChanges()" /> is called.
+    ///     it is not a nullable type, then an exception will be thrown when
+    ///     <c>SaveChanges()</c> is called.
     /// </summary>
     /// <remarks>
     ///     <para>
     ///         If the database has been created from the model using Entity Framework Migrations or the
-    ///         <see cref="DatabaseFacade.EnsureCreated" /> method, then the behavior in the database
+    ///         <c>EnsureCreated()</c> method, then the behavior in the database
     ///         is to generate an error if a foreign key constraint is violated.
     ///     </para>
     ///     <para>
@@ -45,29 +46,30 @@ public enum DeleteBehavior
     ClientSetNull,
 
     /// <summary>
-    ///     For entities being tracked by the <see cref="DbContext" />, the values of foreign key properties in
-    ///     dependent entities are set to null when the related principal is deleted.
+    ///     For entities being tracked by the context, the values of foreign key properties in dependent entities
+    ///     are set to null when the related principal is deleted.
     ///     This helps keep the graph of entities in a consistent state while they are being tracked, such that a
     ///     fully consistent graph can then be written to the database. If a property cannot be set to null because
-    ///     it is not a nullable type, then an exception will be thrown when <see cref="DbContext.SaveChanges()" /> is called.
+    ///     it is not a nullable type, then an exception will be thrown when
+    ///     <c>SaveChanges()</c> is called.
     /// </summary>
     /// <remarks>
     ///     If the database has been created from the model using Entity Framework Migrations or the
-    ///     <see cref="DatabaseFacade.EnsureCreated" /> method, then the behavior in the database
-    ///     is to generate an error if a foreign key constraint is violated.
+    ///     <c>EnsureCreated()</c> method, then the behavior in the database is to generate an error if a foreign key constraint is violated.
     /// </remarks>
     Restrict,
 
     /// <summary>
-    ///     For entities being tracked by the <see cref="DbContext" />, the values of foreign key properties in
+    ///     For entities being tracked by the context, the values of foreign key properties in
     ///     dependent entities are set to null when the related principal is deleted.
     ///     This helps keep the graph of entities in a consistent state while they are being tracked, such that a
     ///     fully consistent graph can then be written to the database. If a property cannot be set to null because
-    ///     it is not a nullable type, then an exception will be thrown when <see cref="DbContext.SaveChanges()" /> is called.
+    ///     it is not a nullable type, then an exception will be thrown when
+    ///     <c>SaveChanges()</c> is called.
     /// </summary>
     /// <remarks>
     ///     If the database has been created from the model using Entity Framework Migrations or the
-    ///     <see cref="DatabaseFacade.EnsureCreated" /> method, then the behavior in the database is
+    ///     <c>EnsureCreated()</c> method, then the behavior in the database is
     ///     the same as is described above for tracked entities. Keep in mind that some databases cannot easily
     ///     support this behavior, especially if there are cycles in relationships, in which case it may
     ///     be better to use <see cref="ClientSetNull" /> which will allow EF to cascade null values
@@ -76,13 +78,13 @@ public enum DeleteBehavior
     SetNull,
 
     /// <summary>
-    ///     For entities being tracked by the <see cref="DbContext" />, dependent entities
+    ///     For entities being tracked by the context, dependent entities
     ///     will be deleted when the related principal is deleted.
     /// </summary>
     /// <remarks>
     ///     <para>
     ///         If the database has been created from the model using Entity Framework Migrations or the
-    ///         <see cref="DatabaseFacade.EnsureCreated" /> method, then the behavior in the database is
+    ///         <c>EnsureCreated()</c> method, then the behavior in the database is
     ///         the same as is described above for tracked entities. Keep in mind that some databases cannot easily
     ///         support this behavior, especially if there are cycles in relationships, in which case it may
     ///         be better to use <see cref="ClientCascade" /> which will allow EF to perform cascade deletes
@@ -96,27 +98,25 @@ public enum DeleteBehavior
     Cascade,
 
     /// <summary>
-    ///     For entities being tracked by the <see cref="DbContext" />, dependent entities
+    ///     For entities being tracked by the context, dependent entities
     ///     will be deleted when the related principal is deleted.
     /// </summary>
     /// <remarks>
     ///     If the database has been created from the model using Entity Framework Migrations or the
-    ///     <see cref="DatabaseFacade.EnsureCreated" /> method, then the behavior in the database
-    ///     is to generate an error if a foreign key constraint is violated.
+    ///     <c>EnsureCreated()</c> method, then the behavior in the database is to generate an error if a foreign key constraint is violated.
     /// </remarks>
     ClientCascade,
 
     /// <summary>
-    ///     For entities being tracked by the <see cref="DbContext" />, the values of foreign key properties in
-    ///     dependent entities are set to null when the related principal is deleted.
+    ///     For entities being tracked by the context, the values of foreign key properties in dependent entities are set to null when the related principal is deleted.
     ///     This helps keep the graph of entities in a consistent state while they are being tracked, such that a
     ///     fully consistent graph can then be written to the database. If a property cannot be set to null because
-    ///     it is not a nullable type, then an exception will be thrown when <see cref="DbContext.SaveChanges()" /> is called.
+    ///     it is not a nullable type, then an exception will be thrown when
+    ///     <c>SaveChanges()</c> is called.
     /// </summary>
     /// <remarks>
     ///     If the database has been created from the model using Entity Framework Migrations or the
-    ///     <see cref="DatabaseFacade.EnsureCreated" /> method, then the behavior in the database
-    ///     is to generate an error if a foreign key constraint is violated.
+    ///     <c>EnsureCreated()</c> method, then the behavior in the database is to generate an error if a foreign key constraint is violated.
     /// </remarks>
     NoAction,
 
@@ -126,15 +126,13 @@ public enum DeleteBehavior
     /// </summary>
     /// <remarks>
     ///     <para>
-    ///         For entities being tracked by the <see cref="DbContext" />, the values of foreign key properties in
-    ///         dependent entities are not changed when the related principal entity is deleted.
+    ///         For entities being tracked by the context, the values of foreign key properties in dependent entities are not changed when the related principal entity is deleted.
     ///         This can result in an inconsistent graph of entities where the values of foreign key properties do
     ///         not match the relationships in the graph.
     ///     </para>
     ///     <para>
     ///         If the database has been created from the model using Entity Framework Migrations or the
-    ///         <see cref="DatabaseFacade.EnsureCreated" /> method, then the behavior in the database
-    ///         is to generate an error if a foreign key constraint is violated.
+    ///         <c>EnsureCreated()</c> method, then the behavior in the database is to generate an error if a foreign key constraint is violated.
     ///     </para>
     /// </remarks>
     ClientNoAction

src/EFCore.Abstractions/DeleteBehaviorAttribute.cs

@@ -0,0 +1,30 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace Microsoft.EntityFrameworkCore;
+
+/// <summary>
+///     Configures the navigation property on the dependent side of a relationship
+///     to indicate how a delete operation is applied to dependent entities
+///     in a relationship when it is deleted or the relationship is severed.
+/// </summary>
+/// <remarks>
+///     See <see href="https://aka.ms/efcore-docs-modeling">Modeling entity types and relationships</see> for more information and examples.
+/// </remarks>
+[AttributeUsage(AttributeTargets.Property)]
+public sealed class DeleteBehaviorAttribute : Attribute
+{
+    /// <summary>
+    ///     Initializes a new instance of the <see cref="DeleteBehaviorAttribute" /> class.
+    /// </summary>
+    /// <param name="behavior">The <see cref="DeleteBehavior" /> to be configured.</param>
+    public DeleteBehaviorAttribute(DeleteBehavior behavior)
+    {
+        this.Behavior = behavior;
+    }
+
+    /// <summary>
+    ///     Gets the <see cref="DeleteBehavior" /> to be configured.
+    /// </summary>
+    public DeleteBehavior Behavior { get; }
+}

src/EFCore/Metadata/Conventions/DeleteBehaviorAttributeConvention.cs

@@ -0,0 +1,111 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace Microsoft.EntityFrameworkCore.Metadata.Conventions;
+
+using Microsoft.EntityFrameworkCore.Diagnostics;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+using Microsoft.EntityFrameworkCore.Metadata.Conventions.Infrastructure;
+
+/// <summary>
+///     A convention that configures the delete behavior based on the <see cref="DeleteBehaviorAttribute" /> applied on the property.
+/// </summary>
+/// <remarks>
+///     See <see href="https://aka.ms/efcore-docs-conventions">Model building conventions</see> for more information and examples.
+/// </remarks>
+public class DeleteBehaviorAttributeConvention : PropertyAttributeConventionBase<DeleteBehaviorAttribute>, INavigationAddedConvention, IForeignKeyPrincipalEndChangedConvention, IModelFinalizingConvention
+{
+    /// <summary>
+    ///     Initializes a new instance of the <see cref="DeleteBehaviorAttributeConvention"/> class.
+    /// </summary>
+    /// <param name="dependencies">Parameter object containing dependencies for this convention.</param>
+    public DeleteBehaviorAttributeConvention(ProviderConventionSetBuilderDependencies dependencies)
+        : base(dependencies)
+    {
+    }
+
+    /// <summary>
+    ///     Called after a navigation is added to the entity type.
+    /// </summary>
+    /// <param name="navigationBuilder">The builder for the navigation.</param>
+    /// <param name="context">Additional information associated with convention execution.</param>
+    public virtual void ProcessNavigationAdded(IConventionNavigationBuilder navigationBuilder, IConventionContext<IConventionNavigationBuilder> context)
+    {
+        var navAttribute = navigationBuilder.Metadata.PropertyInfo?.GetCustomAttribute<DeleteBehaviorAttribute>();
+        if (navAttribute == null)
+        {
+            return;
+        }
+
+        var foreignKey = navigationBuilder.Metadata.ForeignKey;
+        if (!navigationBuilder.Metadata.IsOnDependent && foreignKey.IsUnique)
+        {
+            return;
+        }
+
+        foreignKey.Builder.OnDelete(navAttribute.Behavior, fromDataAnnotation: true);
+    }
+
+    /// <summary>
+    ///     Called after the principal end of a foreign key is changed.
+    /// </summary>
+    /// <param name="relationshipBuilder">The builder for the foreign key.</param>
+    /// <param name="context">Additional information associated with convention execution.</param>
+    public virtual void ProcessForeignKeyPrincipalEndChanged(IConventionForeignKeyBuilder relationshipBuilder, IConventionContext<IConventionForeignKeyBuilder> context)
+    {
+        if (!relationshipBuilder.Metadata.IsUnique)
+        {
+            return;
+        }
+
+        var navigation = relationshipBuilder.Metadata.DependentToPrincipal;
+        var navAttribute = navigation?.PropertyInfo?.GetCustomAttribute<DeleteBehaviorAttribute>();
+        if (navAttribute == null)
+        {
+            return;
+        }
+
+        relationshipBuilder.OnDelete(navAttribute.Behavior, fromDataAnnotation: true);
+    }
+
+    /// <summary>
+    ///     Called when a model is being finalized.
+    /// </summary>
+    /// <param name="modelBuilder">The builder for the model.</param>
+    /// <param name="context">Additional information associated with convention execution.</param>
+    public virtual void ProcessModelFinalizing(IConventionModelBuilder modelBuilder, IConventionContext<IConventionModelBuilder> context)
+    {
+        foreach (var entityType in modelBuilder.Metadata.GetEntityTypes())
+        {
+            foreach (var navigation in entityType.GetNavigations())
+            {
+                var navAttribute = navigation.PropertyInfo?.GetCustomAttribute<DeleteBehaviorAttribute>();
+                if (navAttribute == null)
+                {
+                    return;
+                }
+
+                if (!navigation.IsOnDependent)
+                {
+                    throw new InvalidOperationException(CoreStrings.DeleteBehaviorAttributeOnPrincipalProperty);
+                }
+            }
+        }
+    }
+
+    /// <summary>
+    ///     Called after a property is added to the entity type with an attribute on the associated CLR property or field.
+    /// </summary>
+    /// <param name="propertyBuilder">The builder for the property.</param>
+    /// <param name="attribute">The attribute.</param>
+    /// <param name="clrMember">The member that has the attribute.</param>
+    /// <param name="context">Additional information associated with convention execution.</param>
+    protected override void ProcessPropertyAdded(
+        IConventionPropertyBuilder propertyBuilder,
+        DeleteBehaviorAttribute attribute,
+        MemberInfo clrMember,
+        IConventionContext context)
+    {
+        throw new InvalidOperationException(CoreStrings.DeleteBehaviorAttributeNotOnNavigationProperty);
+    }
+}

src/EFCore/Metadata/Conventions/Infrastructure/ProviderConventionSetBuilder.cs

@@ -116,6 +116,7 @@ public virtual ConventionSet CreateConventionSet()
         var backingFieldAttributeConvention = new BackingFieldAttributeConvention(Dependencies);
         var unicodeAttributeConvention = new UnicodeAttributeConvention(Dependencies);
         var precisionAttributeConvention = new PrecisionAttributeConvention(Dependencies);
+        var deleteBehaviorAttributeConvention = new DeleteBehaviorAttributeConvention(Dependencies);
 
         conventionSet.PropertyAddedConventions.Add(backingFieldAttributeConvention);
         conventionSet.PropertyAddedConventions.Add(backingFieldConvention);
@@ -131,6 +132,7 @@ public virtual ConventionSet CreateConventionSet()
         conventionSet.PropertyAddedConventions.Add(foreignKeyPropertyDiscoveryConvention);
         conventionSet.PropertyAddedConventions.Add(unicodeAttributeConvention);
         conventionSet.PropertyAddedConventions.Add(precisionAttributeConvention);
+        conventionSet.PropertyAddedConventions.Add(deleteBehaviorAttributeConvention);
 
         conventionSet.EntityTypePrimaryKeyChangedConventions.Add(foreignKeyPropertyDiscoveryConvention);
         conventionSet.EntityTypePrimaryKeyChangedConventions.Add(valueGeneratorConvention);
@@ -186,6 +188,7 @@ public virtual ConventionSet CreateConventionSet()
         conventionSet.NavigationAddedConventions.Add(foreignKeyPropertyDiscoveryConvention);
         conventionSet.NavigationAddedConventions.Add(relationshipDiscoveryConvention);
         conventionSet.NavigationAddedConventions.Add(foreignKeyAttributeConvention);
+        conventionSet.NavigationAddedConventions.Add(deleteBehaviorAttributeConvention);
 
         var manyToManyJoinEntityTypeConvention = new ManyToManyJoinEntityTypeConvention(Dependencies);
         conventionSet.SkipNavigationAddedConventions.Add(new NavigationBackingFieldAttributeConvention(Dependencies));
@@ -213,6 +216,7 @@ public virtual ConventionSet CreateConventionSet()
         conventionSet.ForeignKeyPrincipalEndChangedConventions.Add(foreignKeyPropertyDiscoveryConvention);
         conventionSet.ForeignKeyPrincipalEndChangedConventions.Add(requiredNavigationAttributeConvention);
         conventionSet.ForeignKeyPrincipalEndChangedConventions.Add(nonNullableNavigationConvention);
+        conventionSet.ForeignKeyPrincipalEndChangedConventions.Add(deleteBehaviorAttributeConvention);
 
         conventionSet.PropertyNullabilityChangedConventions.Add(foreignKeyPropertyDiscoveryConvention);
 
@@ -241,6 +245,7 @@ public virtual ConventionSet CreateConventionSet()
         conventionSet.ModelFinalizingConventions.Add(new QueryFilterRewritingConvention(Dependencies));
         conventionSet.ModelFinalizingConventions.Add(inversePropertyAttributeConvention);
         conventionSet.ModelFinalizingConventions.Add(backingFieldConvention);
+        conventionSet.ModelFinalizingConventions.Add(deleteBehaviorAttributeConvention);
 
         conventionSet.ModelFinalizedConventions.Add(new RuntimeModelConvention(Dependencies));