Implement IListSource on LocalView and EntityQueryable to further direct data binding

src/EFCore/ChangeTracking/LocalView.cs

@@ -1,6 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System;
 using System.Collections;
 using System.Collections.Generic;
 using System.Collections.ObjectModel;
@@ -46,7 +47,7 @@ namespace Microsoft.EntityFrameworkCore.ChangeTracking
     ///     </para>
     /// </summary>
     /// <typeparam name="TEntity">The type of the entity in the local view.</typeparam>
-    public class LocalView<TEntity> : ICollection<TEntity>, INotifyCollectionChanged, INotifyPropertyChanged, INotifyPropertyChanging
+    public class LocalView<TEntity> : ICollection<TEntity>, INotifyCollectionChanged, INotifyPropertyChanged, INotifyPropertyChanging, IListSource
         where TEntity : class
     {
         private ObservableBackedBindingList<TEntity> _bindingList;
@@ -443,5 +444,26 @@ private void OnCollectionChanged(NotifyCollectionChangedAction action, object it
         /// <returns> The binding list. </returns>
         public virtual BindingList<TEntity> ToBindingList()
             => _bindingList ?? (_bindingList = new ObservableBackedBindingList<TEntity>(ToObservableCollection()));
+
+        /// <summary>
+        ///     <para>
+        ///         This method is called by data binding frameworks when attempting to data bind
+        ///         directly to a <see cref="LocalView{TEntity}" />.
+        ///     </para>
+        ///     <para>
+        ///         This implementation always throws an exception as <see cref="LocalView{TEntity}" /> 
+        ///         does not maintain an ordered list with indexes. Instead call <see cref="ToObservableCollection" /> 
+        ///         for WPF binding, or <see cref="ToBindingList" /> for WinForms.
+        ///     </para>
+        /// </summary>
+        /// <exception cref="NotSupportedException"> Always thrown. </exception>
+        /// <returns> Never returns, always throws an exception. </returns>
+        IList IListSource.GetList() => throw new NotSupportedException(CoreStrings.DataBindingWithIListSource);
+
+        /// <summary>
+        ///     Gets a value indicating whether the collection is a collection of System.Collections.IList objects.
+        ///     Always returns false.
+        /// </summary>
+        bool IListSource.ContainsListCollection => false;
     }
 }

src/EFCore/Query/Internal/EntityQueryable`.cs

@@ -1,10 +1,14 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System;
+using System.Collections;
 using System.Collections.Generic;
+using System.ComponentModel;
 using System.Linq.Expressions;
 using JetBrains.Annotations;
 using Microsoft.EntityFrameworkCore.Utilities;
+using Microsoft.EntityFrameworkCore.Internal;
 using Remotion.Linq;
 
 namespace Microsoft.EntityFrameworkCore.Query.Internal
@@ -13,7 +17,7 @@ namespace Microsoft.EntityFrameworkCore.Query.Internal
     ///     This API supports the Entity Framework Core infrastructure and is not intended to be used
     ///     directly from your code. This API may change or be removed in future releases.
     /// </summary>
-    public class EntityQueryable<TResult> : QueryableBase<TResult>, IAsyncEnumerable<TResult>, IDetachableContext
+    public class EntityQueryable<TResult> : QueryableBase<TResult>, IAsyncEnumerable<TResult>, IDetachableContext, IListSource
     {
         /// <summary>
         ///     This API supports the Entity Framework Core infrastructure and is not intended to be used
@@ -35,10 +39,33 @@ public EntityQueryable([NotNull] IAsyncQueryProvider provider, [NotNull] Express
         {
         }
 
+        /// <summary>
+        ///     This API supports the Entity Framework Core infrastructure and is not intended to be used
+        ///     directly from your code. This API may change or be removed in future releases.
+        /// </summary>
         IAsyncEnumerator<TResult> IAsyncEnumerable<TResult>.GetEnumerator()
             => ((IAsyncQueryProvider)Provider).ExecuteAsync<TResult>(Expression).GetEnumerator();
 
+        /// <summary>
+        ///     This API supports the Entity Framework Core infrastructure and is not intended to be used
+        ///     directly from your code. This API may change or be removed in future releases.
+        /// </summary>
         IDetachableContext IDetachableContext.DetachContext()
             => new EntityQueryable<TResult>(NullAsyncQueryProvider.Instance);
+
+        /// <summary>
+        ///     This API supports the Entity Framework Core infrastructure and is not intended to be used
+        ///     directly from your code. This API may change or be removed in future releases.
+        /// </summary>
+        IList IListSource.GetList()
+        {
+            throw new NotSupportedException(CoreStrings.DataBindingWithIListSource);
+        }
+
+        /// <summary>
+        ///     This API supports the Entity Framework Core infrastructure and is not intended to be used
+        ///     directly from your code. This API may change or be removed in future releases.
+        /// </summary>
+        bool IListSource.ContainsListCollection => false;
     }
 }

test/EFCore.Tests/DbSetTest.cs

@@ -566,6 +566,26 @@ public void Throws_when_using_with_IListSource()
             }
         }
 
+        [Fact]
+        public void Throws_when_using_query_with_IListSource()
+        {
+            using (var context = new EarlyLearningCenter())
+            {
+                Assert.Equal(CoreStrings.DataBindingWithIListSource,
+                    Assert.Throws<NotSupportedException>(() => ((IListSource)context.Gus.Distinct()).GetList()).Message);
+            }
+        }
+
+        [Fact]
+        public void Throws_when_using_Local_with_IListSource()
+        {
+            using (var context = new EarlyLearningCenter())
+            {
+                Assert.Equal(CoreStrings.DataBindingWithIListSource,
+                    Assert.Throws<NotSupportedException>(() => ((IListSource)context.Gus.Local).GetList()).Message);
+            }
+        }
+
         private class Category
         {
             public int Id { get; set; }