Add Subscription#Nack

Author: michaelklishin

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

@@ -187,6 +187,44 @@ public void Ack(BasicDeliverEventArgs evt)
             }
         }
 
+        ///<summary>If LatestEvent is non-null, passes it to
+        ///Nack(BasicDeliverEventArgs, multiple, requeue). Causes LatestEvent to become
+        ///null.</summary>
+        public void Nack(bool multiple, bool requeue)
+        {
+            if (m_latestEvent != null) {
+                Nack(m_latestEvent, multiple, requeue);
+            }
+        }
+
+        ///<summary>If we are not in "noAck" mode, calls
+        ///IModel.BasicNack with the delivery-tag from the passed in
+        ///event; otherwise, sends nothing to the server. In both
+        ///cases, if the passed-in event is the same as LatestEvent
+        ///(by pointer comparison), sets LatestEvent to
+        ///null.</summary>
+        ///<remarks>
+        /// Make sure that this method is only called with events that
+        /// originated from this Subscription - other usage will have
+        /// unpredictable results.
+        ///</remarks>
+        public void Nack(BasicDeliverEventArgs evt,
+                         bool multiple,
+                         bool requeue)
+        {
+            if (evt == null) {
+                return;
+            }
+
+            if (!m_noAck) {
+                m_model.BasicNack(evt.DeliveryTag, multiple, requeue);
+            }
+
+            if (evt == m_latestEvent) {
+                m_latestEvent = null;
+            }
+        }
+
         ///<summary>Retrieves the next incoming delivery in our
         ///subscription queue.</summary>
         ///<remarks>

projects/client/Unit/src/unit/TestMessagePatternsSubscription.cs

@@ -90,5 +90,20 @@ public void TestSubscriptionAck()
             QueueDeclareOk ok = Model.QueueDeclarePassive(q);
             Assert.AreEqual(0, ok.MessageCount);
         }
+
+        [Test]
+        public void TestSubscriptionNack()
+        {
+            Model.BasicQos(0, 1, false);
+            string q = Model.QueueDeclare();
+            Subscription sub = new Subscription(Model, q, false);
+
+            Model.BasicPublish("", q, null, enc.GetBytes("a message"));
+            BasicDeliverEventArgs res = sub.Next();
+            Assert.IsNotNull(res);
+            sub.Nack(false, false);
+            QueueDeclareOk ok = Model.QueueDeclarePassive(q);
+            Assert.AreEqual(0, ok.MessageCount);
+        }
     }
 }