1595 object disposed exception in unit test handle parallel connection attempts (#1610)

Source/MQTTnet/Internal/CancellationTokenSourceExtensions.cs

@@ -0,0 +1,37 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Threading;
+
+namespace MQTTnet.Internal
+{
+    public static class CancellationTokenSourceExtensions
+    {
+        public static bool TryCancel(this CancellationTokenSource cancellationTokenSource, bool throwOnFirstException = false)
+        {
+            if (cancellationTokenSource == null)
+            {
+                return false;
+            }
+
+            try
+            {
+                // Checking the _IsCancellationRequested_ here will not throw an
+                // "ObjectDisposedException" as the getter of the property "Token" will do!
+                if (cancellationTokenSource.IsCancellationRequested)
+                {
+                    return false;
+                }
+
+                cancellationTokenSource.Cancel(throwOnFirstException);
+                return true;
+            }
+            catch (ObjectDisposedException)
+            {
+                return false;
+            }
+        }
+    }
+}