Merge pull request #223 from rabbitmq/rabbitmq-dotnet-client-220

null timers after disposing them to avoid duplicate calls to Dispose

Author: michaelklishin

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

@@ -1061,8 +1061,10 @@ public void HeartbeatReadTimerCallback(object state)
                 {
                     _heartbeatReadTimer.Change(Heartbeat * 1000, Timeout.Infinite);
                 }
-            } catch (ObjectDisposedException ignored)
+            }
+            catch (ObjectDisposedException ignored)
             {
+
                 // timer is already disposed,
                 // e.g. due to shutdown
             }
@@ -1096,7 +1098,8 @@ public void HeartbeatWriteTimerCallback(object state)
                     TerminateMainloop();
                     FinishClose();
                 }
-            } catch (ObjectDisposedException ignored)
+            }
+            catch (ObjectDisposedException ignored)
             {
                 // timer is already disposed,
                 // e.g. due to shutdown
@@ -1105,19 +1108,21 @@ public void HeartbeatWriteTimerCallback(object state)
 
         protected void MaybeStopHeartbeatTimers()
         {
-            MaybeDisposeTimer(_heartbeatReadTimer);
-            MaybeDisposeTimer(_heartbeatWriteTimer);
+            MaybeDisposeTimer(ref _heartbeatReadTimer);
+            MaybeDisposeTimer(ref _heartbeatWriteTimer);
         }
 
-        private void MaybeDisposeTimer(Timer timer)
+        private void MaybeDisposeTimer(ref Timer timer)
         {
             if (timer != null)
             {
                 try
                 {
                     timer.Change(Timeout.Infinite, Timeout.Infinite);
                     timer.Dispose();
-                } catch (ObjectDisposedException ignored)
+                    timer = null;
+                }
+                catch (ObjectDisposedException ignored)
                 {
                     // we are shutting down, ignore
                 }