Perf | Cache common callbacks with a single state parameter (#378)

Author: Wraith2

src/Microsoft.Data.SqlClient/netcore/src/Microsoft/Data/SqlClient/SqlConnection.cs

@@ -90,6 +90,8 @@ private static readonly ConcurrentDictionary<string, IList<string>> _ColumnEncry
                 capacity: 1,
                 comparer: StringComparer.OrdinalIgnoreCase);
 
+        private static readonly Action<object> s_openAsyncCancel = OpenAsyncCancel;
+
         /// <include file='..\..\..\..\..\..\..\doc\snippets\Microsoft.Data.SqlClient\SqlConnection.xml' path='docs/members[@name="SqlConnection"]/ColumnEncryptionKeyCacheTtl/*' />
         public static TimeSpan ColumnEncryptionKeyCacheTtl { get; set; } = TimeSpan.FromHours(2);
 
@@ -1281,7 +1283,7 @@ public override Task OpenAsync(CancellationToken cancellationToken)
                     CancellationTokenRegistration registration = new CancellationTokenRegistration();
                     if (cancellationToken.CanBeCanceled)
                     {
-                        registration = cancellationToken.Register(s => ((TaskCompletionSource<DbConnectionInternal>)s).TrySetCanceled(), completion);
+                        registration = cancellationToken.Register(s_openAsyncCancel, completion);
                     }
                     OpenAsyncRetry retry = new OpenAsyncRetry(this, completion, result, registration);
                     _currentCompletion = new Tuple<TaskCompletionSource<DbConnectionInternal>, Task>(completion, result.Task);
@@ -1302,6 +1304,11 @@ public override Task OpenAsync(CancellationToken cancellationToken)
             }
         }
 
+        private static void OpenAsyncCancel(object state)
+        {
+            ((TaskCompletionSource<DbConnectionInternal>)state).TrySetCanceled();
+        }
+
         /// <include file='..\..\..\..\..\..\..\doc\snippets\Microsoft.Data.SqlClient\SqlConnection.xml' path='docs/members[@name="SqlConnection"]/GetSchema2/*' />
         public override DataTable GetSchema()
         {

src/Microsoft.Data.SqlClient/netcore/src/Microsoft/Data/SqlClient/TdsParserStateObject.cs

@@ -35,6 +35,8 @@ internal enum SnapshottedStateFlags : byte
 
         private const int AttentionTimeoutSeconds = 5;
 
+        private static readonly ContextCallback s_readAdyncCallbackComplete = ReadAsyncCallbackComplete;
+
         // Ticks to consider a connection "good" after a successful I/O (10,000 ticks = 1 ms)
         // The resolution of the timer is typically in the range 10 to 16 milliseconds according to msdn.
         // We choose a value that is smaller than the likely timer resolution, but
@@ -2824,7 +2826,7 @@ public void ReadAsyncCallback(IntPtr key, PacketHandle packet, uint error)
                     {
                         if (_executionContext != null)
                         {
-                            ExecutionContext.Run(_executionContext, (state) => source.TrySetResult(null), null);
+                            ExecutionContext.Run(_executionContext, s_readAdyncCallbackComplete, source);
                         }
                         else
                         {
@@ -2848,6 +2850,12 @@ public void ReadAsyncCallback(IntPtr key, PacketHandle packet, uint error)
             }
         }
 
+        private static void ReadAsyncCallbackComplete(object state)
+        {
+            TaskCompletionSource<object> source = (TaskCompletionSource<object>)state;
+            source.TrySetResult(null);
+        }
+
         protected abstract bool CheckPacket(PacketHandle packet, TaskCompletionSource<object> source);
 
         private void ReadAsyncCallbackCaptureException(TaskCompletionSource<object> source)