Merge pull request #790 from PHOENIXCONTACT/port/pending-elements

Port: Allow reading the number of pending elements in the ParallelOperationsQueue.

Author: 1nf0rmagician

src/Moryx/Threading/ParallelOperationsQueue.cs

@@ -41,6 +41,11 @@ public class ParallelOperationsQueue<TElement>
         /// </summary>
         public ILogger ErrorLogger { get; }
 
+        /// <summary>
+        /// Provide the number of unprocessed elements in the queue
+        /// </summary>
+        public int PendingElements => _pendingElements;
+
         /// <summary>
         /// Create a new <see cref="Threading.ParallelOperations.EventDecoupler{TEventArgs}"/> to decouple a single listener from an event
         /// </summary>