Add event for processed application message (managed client only)

Frameworks/MQTTnet.NetStandard/ManagedClient/ApplicationMessageProcessedEventArgs.cs

@@ -0,0 +1,19 @@
+using System;
+
+namespace MQTTnet.ManagedClient
+{
+    public class ApplicationMessageProcessedEventArgs : EventArgs
+    {
+        public ApplicationMessageProcessedEventArgs(MqttApplicationMessage applicationMessage, Exception exception)
+        {
+            ApplicationMessage = applicationMessage ?? throw new ArgumentNullException(nameof(applicationMessage));
+            Exception = exception;
+        }
+
+        public MqttApplicationMessage ApplicationMessage { get; }
+        public Exception Exception { get; }
+
+        public bool HasFailed => Exception != null;
+        public bool HasSucceeded => Exception == null;
+    }
+}

Frameworks/MQTTnet.NetStandard/ManagedClient/IManagedMqttClient.cs

@@ -12,6 +12,8 @@ namespace MQTTnet.ManagedClient
         event EventHandler<MqttClientConnectedEventArgs> Connected;
         event EventHandler<MqttClientDisconnectedEventArgs> Disconnected;
 
+        event EventHandler<ApplicationMessageProcessedEventArgs> ApplicationMessageProcessed;
+
         Task StartAsync(IManagedMqttClientOptions options);
         Task StopAsync();
 

Frameworks/MQTTnet.NetStandard/ManagedClient/ManagedMqttClient.cs

@@ -43,6 +43,7 @@ namespace MQTTnet.ManagedClient
         public event EventHandler<MqttClientConnectedEventArgs> Connected;
         public event EventHandler<MqttClientDisconnectedEventArgs> Disconnected;
         public event EventHandler<MqttApplicationMessageReceivedEventArgs> ApplicationMessageReceived;
+        public event EventHandler<ApplicationMessageProcessedEventArgs> ApplicationMessageProcessed;
 
         public async Task StartAsync(IManagedMqttClientOptions options)
         {
@@ -245,6 +246,7 @@ namespace MQTTnet.ManagedClient
 
         private async Task TryPublishQueuedMessageAsync(MqttApplicationMessage message)
         {
+            Exception transmitException = null;
             try
             {
                 await _mqttClient.PublishAsync(message).ConfigureAwait(false);
@@ -256,6 +258,8 @@ namespace MQTTnet.ManagedClient
             }
             catch (MqttCommunicationException exception)
             {
+                transmitException = exception;
+
                 _logger.Warning<ManagedMqttClient>(exception, "Publishing application message failed.");
 
                 if (message.QualityOfServiceLevel > MqttQualityOfServiceLevel.AtMostOnce)
@@ -265,8 +269,13 @@ namespace MQTTnet.ManagedClient
             }
             catch (Exception exception)
             {
+                transmitException = exception;
                 _logger.Error<ManagedMqttClient>(exception, "Unhandled exception while publishing queued application message.");
             }
+            finally
+            {
+                ApplicationMessageProcessed?.Invoke(this, new ApplicationMessageProcessedEventArgs(message, transmitException));
+            }
         }
 
         private async Task PushSubscriptionsAsync()