fixed #743

Build/MQTTnet.nuspec

@@ -17,6 +17,7 @@
 * [Server] Refactoring of server certificate password classes (BREAKING CHANGE!).
 * [Server] Fixed an issue with empty server certificate passwords (thanks to @SeppPenner).
 * [MQTTnet.Server] Added support for certificate passwords (BREAKING CHANGE IN CONFIG!)
+* [MQTTnet.AspNetCore] fixed an issue with mqtt V5 package serialization (#743)
     </releaseNotes>
     <copyright>Copyright Christian Kratky 2016-2019</copyright>
     <tags>MQTT Message Queue Telemetry Transport MQTTClient MQTTServer Server MQTTBroker Broker NETStandard IoT InternetOfThings Messaging Hardware Arduino Sensor Actuator M2M ESP Smart Home Cities Automation Xamarin</tags> 

Source/MQTTnet.AspnetCore/SpanBasedMqttPacketWriter.cs

@@ -64,7 +64,6 @@ namespace MQTTnet.AspNetCore
 
             GrowIfNeeded(propertyWriter.Length);
             Write(propertyWriter.GetBuffer(), 0, propertyWriter.Length);
-            Commit(propertyWriter.Length);
         }
 
         public void Write(byte[] payload, int start, int length)

Tests/MQTTnet.Core.Tests/MqttPacketSerializer_Tests.cs

@@ -8,6 +8,7 @@ using Microsoft.VisualStudio.TestTools.UnitTesting;
 using MQTTnet.Adapter;
 using MQTTnet.Formatter;
 using MQTTnet.Formatter.V3;
+using MQTTnet.Formatter.V5;
 using MQTTnet.Internal;
 using MQTTnet.Packets;
 using MQTTnet.Protocol;
@@ -258,6 +259,26 @@ namespace MQTTnet.Tests
             Assert.IsTrue(deserialized.Properties.UserProperties.Any(x => x.Name == "Foo"));
         }
 
+
+        [TestMethod]
+        public void SerializeV500_MqttPublishPacket_CorrelationData()
+        {
+            var data = "123456789";
+            var req = new MqttApplicationMessageBuilder()
+                      .WithTopic("Foo")
+                      .WithResponseTopic($"_")
+                      .WithCorrelationData(Guid.NewGuid().ToByteArray())
+                      .WithPayload(data)
+                      .WithQualityOfServiceLevel(MqttQualityOfServiceLevel.AtMostOnce)
+                      .Build();
+
+            var p = new MqttV500DataConverter().CreatePublishPacket(req);
+
+            var deserialized = Roundtrip(p, MqttProtocolVersion.V500);
+
+            Assert.IsTrue(p.Payload.SequenceEqual(deserialized.Payload));
+        }
+
         [TestMethod]
         public void DeserializeV311_MqttPublishPacket()
         {