"Don't directly throw Exception" System.Threading.Tasks.Dataflow (#26052)

* Don't directly throw Exception

* Don't directly throw Exception

* fix exception message

Author: MarcoRossignoli

src/System.Threading.Tasks.Dataflow/src/Base/DataflowBlock.cs

@@ -1347,13 +1347,12 @@ private void CleanupAndComplete(ReceiveCoreByLinkingCleanupReason reason)
                         if (_receivedException == null) _receivedException = CreateExceptionForTimeout();
                         goto case ReceiveCoreByLinkingCleanupReason.SourceProtocolError;
                     case ReceiveCoreByLinkingCleanupReason.SourceProtocolError:
-                    case ReceiveCoreByLinkingCleanupReason.ErrorDuringCleanup:
-                        Debug.Assert(_receivedException != null, "We need an exception with which to fault the task.");
+                    case ReceiveCoreByLinkingCleanupReason.ErrorDuringCleanup:                        
                         System.Threading.Tasks.Task.Factory.StartNew(state =>
                         {
                             // Complete with the received exception
                             var target = (ReceiveTarget<T>)state;
-                            try { target.TrySetException(target._receivedException ?? new Exception()); }
+                            try { target.TrySetException(target._receivedException ?? new InvalidOperationException(SR.InvalidOperation_ErrorDuringCleanup)); }
                             catch (ObjectDisposedException) { /* benign race if returned task is already disposed */ }
                         }, this, CancellationToken.None, TaskCreationOptions.None, TaskScheduler.Default);
                         break;

src/System.Threading.Tasks.Dataflow/src/Resources/Strings.resx

@@ -97,4 +97,7 @@
   <data name="ConcurrentCollection_SyncRoot_NotSupported" xml:space="preserve">
     <value>The SyncRoot property may not be used for the synchronization of concurrent collections.</value>
   </data>
+  <data name="InvalidOperation_ErrorDuringCleanup" xml:space="preserve">
+    <value>An error occurred while linking up the target or during the cleanup after completion.</value>
+  </data>
 </root>