Make NetMQPoller implement ISynchronizeInvoke.

This interface is used in several APIs where synchronisation is offered, especially those which have been around for a long time in the BCL such as WinForms, WebForms, System.Timers.Timer and System.Diagnostics.Process.

The implementation utilises the TaskScheduler, and as such is not available in the .NET 3.5 build.

src/NetMQ.Tests/NetMQPollerTest.cs

@@ -136,7 +136,7 @@ public void AddSocketDuringWork()
                 poller.RunAsync();
 
                 dealer1.SendFrame("1");
-                Assert.IsTrue(signal1.WaitOne(300));                
+                Assert.IsTrue(signal1.WaitOne(300));
 
                 dealer2.SendFrame("2");
                 Assert.IsTrue(signal2.WaitOne(300));
@@ -799,7 +799,7 @@ public void NativeSocket()
 
         #endregion
 
-        #region Scheduling tests
+        #region TaskScheduler tests
 
 #if !NET35
         [Test]
@@ -931,5 +931,33 @@ public void TwoThreads()
 #endif
 
         #endregion
+
+        #region ISynchronizeInvoke tests
+
+#if !NET35
+        [Test]
+        public void ISynchronizeInvokeWorks()
+        {
+            using (var poller = new NetMQPoller())
+            using (var signal = new ManualResetEvent(false))
+            using (var timer = new System.Timers.Timer { AutoReset = false, Interval = 100, SynchronizingObject = poller, Enabled = true })
+            {
+                var isCorrectThread = false;
+
+                poller.RunAsync();
+
+                timer.Elapsed += (sender, args) =>
+                {
+                    isCorrectThread = poller.CanExecuteTaskInline;
+                    Assert.True(signal.Set());
+                };
+
+                Assert.True(signal.WaitOne(TimeSpan.FromSeconds(2)));
+                Assert.True(isCorrectThread);
+            }
+        }
+#endif
+
+#endregion
     }
 }

src/NetMQ/NetMQPoller.cs

@@ -9,6 +9,7 @@
 using NetMQ.Core.Utils;
 #if !NET35
 using System.Threading.Tasks;
+using System.ComponentModel;
 #endif
 
 using Switch = NetMQ.Core.Utils.Switch;
@@ -17,7 +18,7 @@ namespace NetMQ
 {
     public sealed class NetMQPoller :
 #if !NET35
-        TaskScheduler,
+        TaskScheduler, ISynchronizeInvoke,
 #endif
         INetMQPoller, ISocketPollableCollection, IEnumerable, IDisposable
     {
@@ -109,7 +110,7 @@ protected override void QueueTask(Task task)
             m_tasksQueue.Enqueue(task);
         }
 
-        private void Run(Action action)
+        private void Run([NotNull] Action action)
         {
             if (CanExecuteTaskInline)
                 action();
@@ -528,7 +529,7 @@ public void Dispose()
                 m_switch.WaitForOff();
                 Debug.Assert(!IsRunning);
             }
-            
+
             m_stopSignaler.Dispose();
 #if !NET35
             m_tasksQueue.Dispose();
@@ -542,6 +543,40 @@ public void Dispose()
 
         #endregion
 
+        #region ISynchronizeInvoke
+
+#if !NET35
+        IAsyncResult ISynchronizeInvoke.BeginInvoke(Delegate method, object[] args)
+        {
+            var task = new Task<object>(() => method.DynamicInvoke(args));
+            task.Start(this);
+            return task;
+        }
+
+        object ISynchronizeInvoke.EndInvoke(IAsyncResult result)
+        {
+            var task = (Task<object>)result;
+            return task.Result;
+        }
+
+        object ISynchronizeInvoke.Invoke(Delegate method, object[] args)
+        {
+            if (CanExecuteTaskInline)
+                return method.DynamicInvoke(args);
+
+            var task = new Task<object>(() => method.DynamicInvoke(args));
+            task.Start(this);
+            return task.Result;
+        }
+
+        bool ISynchronizeInvoke.InvokeRequired
+        {
+            get { return !CanExecuteTaskInline; }
+        }
+#endif
+
+        #endregion
+
         #region Synchronisation context
 
 #if !NET35