Imported Upstream version 4.6.0.125

Former-commit-id: a2155e9bd80020e49e72e86c44da02a8ac0e57a4

mcs/class/referencesource/System.Data/Microsoft/SqlServer/Server/SmiEventSink_DeferedProcessing.cs

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+//------------------------------------------------------------------------------
+// <copyright file="SmiEventSink_DeferedProcessing.cs" company="Microsoft">
+//     Copyright (c) Microsoft Corporation.  All rights reserved.
+// </copyright>
+// <owner current="true" primary="true">[....]</owner>
+// <owner current="true" primary="false">[....]</owner>
+//------------------------------------------------------------------------------
+
+namespace Microsoft.SqlServer.Server {
+
+    using System.Data.Sql;
+    using System.Data.SqlClient;
+    using System.Diagnostics;
+
+    // This class exists purely to defer processing of messages until a later time.
+    //  It is designed to allow calling common code that interacts with the SMI layers
+    //  without throwing or otherwise processing messages in the sink until later on.
+    //
+    //  Main example:
+    //      SqlCommand.ExecuteNonQuerySmi calls EventStream.ProcessEvent with it's command event sink (CES)
+    //          ProcessEvent calls OnParametersAvailable on the CES
+    //              OnParametersAvailable sets up a deferedprocessing event sink (DPES) with the CES as its parent
+    //              OnParametersAvailable calls ValueUtils to extract param values passing the DPES
+    //                  ValueUtils calls Smi passing DPES
+    //                      Smi may call MessagePosted, which will send a message up the sink parent chain and save it.
+    //                  ValueUtils calls ProcessMessagesAndThrow on DPES, which skips handling
+    //      ... return up the stack ...
+    //      SqlCommand.ExecuteNonQuerySmi calls CES.ProcessMessagesAndThrow, which handles the messages
+    //              sent from the Smi value extraction code.
+    //
+    //  IMPORTANT: Code that uses the DeferedProccess event sink is responsible for ensuring that
+    //  these messages ARE processed at some point.
+    internal class SmiEventSink_DeferedProcessing : SmiEventSink_Default {
+        internal SmiEventSink_DeferedProcessing ( SmiEventSink parent ) : base(parent) {
+        }
+
+        protected override void DispatchMessages(bool ignoreNonFatalMessages) {
+            // Skip processing messages.  Since messages are sent to parent and calling code will call 
+            //  ProcessMessages against parent, messages ARE NOT LOST!
+        }
+    }
+}
+