Generalize interceptors and add connection and transaction interception

Registration of interceptors is now command and moved to core:
```C#
protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
    optionsBuilder
        .UseSqlite("DataSource=Test.db")
        .AddInterceptors(new MyRelationalInterceptor(), new MyLoggingInterceptor());
}

```

Creating chains (essentially multi-dispatch) is handled automatically, with a mechanism for new interceptors to integrate with the functionality.

Also, added a lot of async paths that will be needed for new ADO.NET async methods. Part of #15917

src/EFCore.Design/Design/DesignTimeServiceCollectionExtensions.cs

@@ -6,6 +6,7 @@
 using JetBrains.Annotations;
 using Microsoft.EntityFrameworkCore.Design.Internal;
 using Microsoft.EntityFrameworkCore.Diagnostics;
+using Microsoft.EntityFrameworkCore.Diagnostics.Internal;
 using Microsoft.EntityFrameworkCore.Infrastructure;
 using Microsoft.EntityFrameworkCore.Internal;
 using Microsoft.EntityFrameworkCore.Metadata;
@@ -56,7 +57,6 @@ public static IServiceCollection AddEntityFrameworkDesignTimeServices(
                 .AddSingleton<ProviderCodeGeneratorDependencies>()
                 .AddSingleton<TypeMappingSourceDependencies>()
                 .AddSingleton<RelationalTypeMappingSourceDependencies>()
-                .AddSingleton<InterceptorsDependencies>()
                 .AddSingleton<ValueConverterSelectorDependencies>()
                 .AddSingleton<ICandidateNamingService, CandidateNamingService>()
                 .AddSingleton<ICSharpDbContextGenerator, CSharpDbContextGenerator>()

src/EFCore.InMemory/Storage/Internal/InMemoryTransaction.cs

@@ -2,6 +2,8 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
+using System.Threading;
+using System.Threading.Tasks;
 using Microsoft.EntityFrameworkCore.Storage;
 
 namespace Microsoft.EntityFrameworkCore.InMemory.Storage.Internal
@@ -42,6 +44,24 @@ public virtual void Rollback()
         {
         }
 
+        /// <summary>
+        ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
+        ///     the same compatibility standards as public APIs. It may be changed or removed without notice in
+        ///     any release. You should only use it directly in your code with extreme caution and knowing that
+        ///     doing so can result in application failures when updating to a new Entity Framework Core release.
+        /// </summary>
+        public virtual Task CommitAsync(CancellationToken cancellationToken = default)
+            => Task.CompletedTask;
+
+        /// <summary>
+        ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
+        ///     the same compatibility standards as public APIs. It may be changed or removed without notice in
+        ///     any release. You should only use it directly in your code with extreme caution and knowing that
+        ///     doing so can result in application failures when updating to a new Entity Framework Core release.
+        /// </summary>
+        public virtual Task RollbackAsync(CancellationToken cancellationToken = default)
+            => Task.CompletedTask;
+
         /// <summary>
         ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
         ///     the same compatibility standards as public APIs. It may be changed or removed without notice in

src/EFCore.Relational/Diagnostics/ConnectionEndEventData.cs

@@ -19,30 +19,22 @@ public class ConnectionEndEventData : ConnectionEventData
         /// </summary>
         /// <param name="eventDefinition"> The event definition. </param>
         /// <param name="messageGenerator"> A delegate that generates a log message for this event. </param>
-        /// <param name="connection">
-        ///     The <see cref="DbConnection" />.
-        /// </param>
-        /// <param name="connectionId">
-        ///     A correlation ID that identifies the <see cref="DbConnection" /> instance being used.
-        /// </param>
-        /// <param name="async">
-        ///     Indicates whether or not the operation is happening asynchronously.
-        /// </param>
-        /// <param name="startTime">
-        ///     The start time of this event.
-        /// </param>
-        /// <param name="duration">
-        ///     The duration this event.
-        /// </param>
+        /// <param name="connection"> The <see cref="DbConnection" />. </param>
+        /// <param name="context"> The <see cref="DbContext" /> currently being used, to null if not known. </param>
+        /// <param name="connectionId"> A correlation ID that identifies the <see cref="DbConnection" /> instance being used. </param>
+        /// <param name="async"> Indicates whether or not the operation is happening asynchronously. </param>
+        /// <param name="startTime"> The start time of this event. </param>
+        /// <param name="duration"> The duration this event. </param>
         public ConnectionEndEventData(
             [NotNull] EventDefinitionBase eventDefinition,
             [NotNull] Func<EventDefinitionBase, EventData, string> messageGenerator,
             [NotNull] DbConnection connection,
+            [CanBeNull] DbContext context,
             Guid connectionId,
             bool async,
             DateTimeOffset startTime,
             TimeSpan duration)
-            : base(eventDefinition, messageGenerator, connection, connectionId, async, startTime)
+            : base(eventDefinition, messageGenerator, connection, context, connectionId, async, startTime)
             => Duration = duration;
 
         /// <summary>

src/EFCore.Relational/Diagnostics/ConnectionErrorEventData.cs

@@ -18,34 +18,24 @@ public class ConnectionErrorEventData : ConnectionEndEventData, IErrorEventData
         /// </summary>
         /// <param name="eventDefinition"> The event definition. </param>
         /// <param name="messageGenerator"> A delegate that generates a log message for this event. </param>
-        /// <param name="connection">
-        ///     The <see cref="DbConnection" />.
-        /// </param>
-        /// <param name="connectionId">
-        ///     A correlation ID that identifies the <see cref="DbConnection" /> instance being used.
-        /// </param>
-        /// <param name="exception">
-        ///     The exception that was thrown when the connection failed.
-        /// </param>
-        /// <param name="async">
-        ///     Indicates whether or not the operation is happening asynchronously.
-        /// </param>
-        /// <param name="startTime">
-        ///     The start time of this event.
-        /// </param>
-        /// <param name="duration">
-        ///     The duration this event.
-        /// </param>
+        /// <param name="connection"> The <see cref="DbConnection" />. </param>
+        /// <param name="context"> The <see cref="DbContext" /> currently being used, to null if not known. </param>
+        /// <param name="connectionId">A correlation ID that identifies the <see cref="DbConnection" /> instance being used. </param>
+        /// <param name="exception"> The exception that was thrown when the connection failed. </param>
+        /// <param name="async"> Indicates whether or not the operation is happening asynchronously. </param>
+        /// <param name="startTime"> The start time of this event. </param>
+        /// <param name="duration"> The duration this event.  </param>
         public ConnectionErrorEventData(
             [NotNull] EventDefinitionBase eventDefinition,
             [NotNull] Func<EventDefinitionBase, EventData, string> messageGenerator,
             [NotNull] DbConnection connection,
+            [CanBeNull] DbContext context,
             Guid connectionId,
             [NotNull] Exception exception,
             bool async,
             DateTimeOffset startTime,
             TimeSpan duration)
-            : base(eventDefinition, messageGenerator, connection, connectionId, async, startTime, duration)
+            : base(eventDefinition, messageGenerator, connection, context, connectionId, async, startTime, duration)
             => Exception = exception;
 
         /// <summary>

src/EFCore.Relational/Diagnostics/ConnectionEventData.cs

@@ -12,33 +12,27 @@ namespace Microsoft.EntityFrameworkCore.Diagnostics
     ///     The <see cref="DiagnosticSource" /> event payload base class for
     ///     <see cref="RelationalEventId" /> connection events.
     /// </summary>
-    public class ConnectionEventData : EventData
+    public class ConnectionEventData : DbContextEventData
     {
         /// <summary>
         ///     Constructs the event payload.
         /// </summary>
         /// <param name="eventDefinition"> The event definition. </param>
         /// <param name="messageGenerator"> A delegate that generates a log message for this event. </param>
-        /// <param name="connection">
-        ///     The <see cref="DbConnection" />.
-        /// </param>
-        /// <param name="connectionId">
-        ///     A correlation ID that identifies the <see cref="DbConnection" /> instance being used.
-        /// </param>
-        /// <param name="async">
-        ///     Indicates whether or not the operation is happening asynchronously.
-        /// </param>
-        /// <param name="startTime">
-        ///     The start time of this event.
-        /// </param>
+        /// <param name="connection"> The <see cref="DbConnection" />. </param>
+        /// <param name="context"> The <see cref="DbContext" /> currently being used, to null if not known. </param>
+        /// <param name="connectionId"> A correlation ID that identifies the <see cref="DbConnection" /> instance being used. </param>
+        /// <param name="async"> Indicates whether or not the operation is happening asynchronously. </param>
+        /// <param name="startTime"> The start time of this event. </param>
         public ConnectionEventData(
             [NotNull] EventDefinitionBase eventDefinition,
             [NotNull] Func<EventDefinitionBase, EventData, string> messageGenerator,
             [NotNull] DbConnection connection,
+            [CanBeNull] DbContext context,
             Guid connectionId,
             bool async,
             DateTimeOffset startTime)
-            : base(eventDefinition, messageGenerator)
+            : base(eventDefinition, messageGenerator, context)
         {
             Connection = connection;
             ConnectionId = connectionId;

src/EFCore.Relational/Diagnostics/DataReaderDisposingEventData.cs

@@ -11,49 +11,35 @@ namespace Microsoft.EntityFrameworkCore.Diagnostics
     /// <summary>
     ///     <see cref="DiagnosticSource" /> event payload for <see cref="RelationalEventId.DataReaderDisposing" />.
     /// </summary>
-    public class DataReaderDisposingEventData : EventData
+    public class DataReaderDisposingEventData : DbContextEventData
     {
         /// <summary>
         ///     Constructs a <see cref="DiagnosticSource" /> event payload for <see cref="RelationalEventId.DataReaderDisposing" />.
         /// </summary>
         /// <param name="eventDefinition"> The event definition. </param>
         /// <param name="messageGenerator"> A delegate that generates a log message for this event. </param>
-        /// <param name="command">
-        ///     The <see cref="DbCommand" /> that created the reader.
-        /// </param>
-        /// <param name="dataReader">
-        ///     The <see cref="DbDataReader" /> that is being disposed.
-        /// </param>
-        /// <param name="commandId">
-        ///     A correlation ID that identifies the <see cref="DbCommand" /> instance being used.
-        /// </param>
-        /// <param name="connectionId">
-        ///     A correlation ID that identifies the <see cref="DbConnection" /> instance being used.
-        /// </param>
-        /// <param name="recordsAffected">
-        ///     Gets the number of rows changed, inserted, or deleted by execution of the SQL statement.
-        /// </param>
-        /// <param name="readCount">
-        ///     Gets the number of read operations performed by this reader.
-        /// </param>
-        /// <param name="startTime">
-        ///     The start time of this event.
-        /// </param>
-        /// <param name="duration">
-        ///     The duration this event.
-        /// </param>
+        /// <param name="command"> The <see cref="DbCommand" /> that created the reader. </param>
+        /// <param name="dataReader"> The <see cref="DbDataReader" /> that is being disposed. </param>
+        /// <param name="context"> The <see cref="DbContext" /> currently being used, to null if not known. </param>
+        /// <param name="commandId">A correlation ID that identifies the <see cref="DbCommand" /> instance being used. </param>
+        /// <param name="connectionId">A correlation ID that identifies the <see cref="DbConnection" /> instance being used. </param>
+        /// <param name="recordsAffected">Gets the number of rows changed, inserted, or deleted by execution of the SQL statement. </param>
+        /// <param name="readCount">Gets the number of read operations performed by this reader. </param>
+        /// <param name="startTime">The start time of this event. </param>
+        /// <param name="duration">The duration this event. </param>
         public DataReaderDisposingEventData(
             [NotNull] EventDefinitionBase eventDefinition,
             [NotNull] Func<EventDefinitionBase, EventData, string> messageGenerator,
             [NotNull] DbCommand command,
             [NotNull] DbDataReader dataReader,
+            [CanBeNull] DbContext context,
             Guid commandId,
             Guid connectionId,
             int recordsAffected,
             int readCount,
             DateTimeOffset startTime,
             TimeSpan duration)
-            : base(eventDefinition, messageGenerator)
+            : base(eventDefinition, messageGenerator, context)
         {
             Command = command;
             DataReader = dataReader;

src/EFCore.Relational/Diagnostics/DbCommandInterceptor.cs

@@ -1,13 +1,9 @@
 // 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.Collections.Generic;
 using System.Data.Common;
-using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
-using JetBrains.Annotations;
-using Microsoft.EntityFrameworkCore.Utilities;
 
 namespace Microsoft.EntityFrameworkCore.Diagnostics
 {
@@ -19,40 +15,6 @@ namespace Microsoft.EntityFrameworkCore.Diagnostics
     /// </summary>
     public abstract class DbCommandInterceptor : IDbCommandInterceptor
     {
-        /// <summary>
-        ///     <para>
-        ///         Chains the given <see cref="IDbCommandInterceptor" /> instances into a chain that will
-        ///         call each in order.
-        ///     </para>
-        ///     <para>
-        ///         If only a single interceptor is supplied, then it is simply returned.
-        ///     </para>
-        /// </summary>
-        /// <param name="interceptors"> The interceptors to chain. </param>
-        /// <returns> An interceptor that calls each of the given interceptors in order. </returns>
-        public static IDbCommandInterceptor CreateChain([NotNull] IEnumerable<IDbCommandInterceptor> interceptors)
-            => CreateChain(Check.NotNull(interceptors, nameof(interceptors)).ToArray());
-
-        /// <summary>
-        ///     <para>
-        ///         Chains the given <see cref="IDbCommandInterceptor" /> instances into a chain that will
-        ///         call each in order.
-        ///     </para>
-        ///     <para>
-        ///         If only a single interceptor is supplied, then it is simply returned.
-        ///     </para>
-        /// </summary>
-        /// <param name="interceptors"> The interceptors to chain. </param>
-        /// <returns> An interceptor that calls each of the given interceptors in order. </returns>
-        public static IDbCommandInterceptor CreateChain([NotNull] params IDbCommandInterceptor[] interceptors)
-        {
-            Check.NotNull(interceptors, nameof(interceptors));
-
-            return interceptors.Length == 1
-                ? interceptors[0]
-                : new CompositeDbCommandInterceptor(interceptors);
-        }
-
         /// <summary>
         ///     Called just before EF intends to call <see cref="DbCommand.ExecuteReader()" />.
         /// </summary>
@@ -389,5 +351,28 @@ public virtual Task CommandFailedAsync(
             CommandErrorEventData eventData,
             CancellationToken cancellationToken = default)
             => Task.CompletedTask;
+
+        /// <summary>
+        ///     Called when execution of a <see cref="DbDataReader"/> is about to be disposed. />.
+        /// </summary>
+        /// <param name="command"> The command. </param>
+        /// <param name="eventData"> Contextual information about the command and reader. </param>
+        /// <param name="result">
+        ///     The current result, or null if no result yet exists.
+        ///     This value will be non-null if some previous interceptor suppressed execution by returning a result from
+        ///     its implementation of this method.
+        ///     This value is typically used as the return value for the implementation of this method.
+        /// </param>
+        /// <returns>
+        ///     If null, then EF will dispose the reader as normal.
+        ///     If non-null, then disposing the reader is suppressed.
+        ///     A normal implementation of this method for any interceptor that is not attempting to change the result
+        ///     is to return the <paramref name="result" /> value passed in.
+        /// </returns>
+        public virtual InterceptionResult? DataReaderDisposing(
+            DbCommand command,
+            DataReaderDisposingEventData eventData,
+            InterceptionResult? result)
+            => result;
     }
 }