Make Subscription#Next return null/false when underlying channel is closed

Author: michaelklishin

projects/client/RabbitMQ.Client/src/client/api/IModel.cs

@@ -126,11 +126,15 @@ public interface IModel: IDisposable
         ///otherwise.</summary>
         ShutdownEventArgs CloseReason { get; }
 
-        ///<summary>Returns true if the session is still in a state
+        ///<summary>Returns true if the model is still in a state
         ///where it can be used. Identical to checking if CloseReason
         ///== null.</summary>
         bool IsOpen { get; }
 
+        ///<summary>Returns true if the model is no longer in a state
+        ///where it can be used.</summary>
+        bool IsClosed { get; }
+
         ///<summary>When in confirm mode, return the sequence number
         ///of the next message to be published.</summary>
         ulong NextPublishSeqNo { get; }

projects/client/RabbitMQ.Client/src/client/impl/ModelBase.cs

@@ -522,6 +522,15 @@ public bool IsOpen
             }
         }
 
+        public bool IsClosed
+        {
+            get
+            {
+                return !IsOpen;
+            }
+        }
+
+
         public ulong NextPublishSeqNo
         {
             get

projects/client/RabbitMQ.Client/src/client/messagepatterns/Subscription.cs

@@ -212,7 +212,7 @@ public BasicDeliverEventArgs Next()
                 // from under us by the operation of Close() from
                 // another thread.
                 QueueingBasicConsumer consumer = m_consumer;
-                if (consumer == null) {
+                if (consumer == null || m_model.IsClosed) {
                     // Closed!
                     m_latestEvent = null;
                 } else {
@@ -275,9 +275,11 @@ public bool Next(int millisecondsTimeout, out BasicDeliverEventArgs result)
                 // from under us by the operation of Close() from
                 // another thread.
                 QueueingBasicConsumer consumer = m_consumer;
-                if (consumer == null) {
+                if (consumer == null || m_model.IsClosed) {
                     // Closed!
                     m_latestEvent = null;
+                    result = null;
+                    return false;
                 } else {
                     BasicDeliverEventArgs qValue;
                     if (!consumer.Queue.Dequeue(millisecondsTimeout, out qValue)) {