Moved check on Options.ValidateFeatures below ThrowIf methods to prev…

…ent NullReferenceException (#1800) * Moved check on Options.ValidateFeatures below ThrowIf methods to prevent NullReferenceException * Add Unit Test * Update ReleaseNotes.md --------- Co-authored-by: Christian <[email protected]>
dotnet · Aug 13, 2023 · b1dc860 · b1dc860
1 parent 1018986
commit b1dc860
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Showing 3 changed files with 26 additions and 3 deletions.
diff --git a/.github/workflows/ReleaseNotes.md b/.github/workflows/ReleaseNotes.md
@@ -1,4 +1,5 @@
 * [Client] Fixed _PlatformNotSupportedException_ when using Blazor (#1755, thanks to @Nickztar).
+* [Client] Fixed _NullReferenceException_ when performing several actions when not connected (#1800, thanks to @ramonsmits).
 * [Server] Fixed _NullReferenceException_ in retained messages management (#1762, thanks to @logicaloud).
 * [Server] Exposed new option which allows disabling packet fragmentation (#1753).
 * [Server] Expired sessions will no longer be used when a client connects (#1756).
diff --git a/Source/MQTTnet.Tests/Clients/MqttClient/MqttClient_Connection_Tests.cs b/Source/MQTTnet.Tests/Clients/MqttClient/MqttClient_Connection_Tests.cs
@@ -196,5 +196,27 @@ public async Task Return_Non_Success()
                 Assert.AreEqual(response.UserProperties[0].Value, "Value");
             }
         }
+
+        [TestMethod]
+        public async Task Throw_Proper_Exception_When_Not_Connected()
+        {
+            try
+            {
+                var mqttFactory = new MqttFactory();
+                using (var mqttClient = mqttFactory.CreateMqttClient())
+                {
+                    await mqttClient.SubscribeAsync("test", MqttQualityOfServiceLevel.AtLeastOnce);
+                }
+            }
+            catch (MqttCommunicationException exception)
+            {
+                if (exception.Message == "The client is not connected.")
+                {
+                    return;
+                }
+            }
+
+            Assert.Fail();
+        }
     }
 }
diff --git a/Source/MQTTnet/Client/MqttClient.cs b/Source/MQTTnet/Client/MqttClient.cs
@@ -321,14 +321,14 @@ public async Task<MqttClientSubscribeResult> SubscribeAsync(MqttClientSubscribeO
                 MqttTopicValidator.ThrowIfInvalidSubscribe(topicFilter.Topic);
             }
 
+            ThrowIfDisposed();
+            ThrowIfNotConnected();
+
             if (Options.ValidateFeatures)
             {
                 MqttClientSubscribeOptionsValidator.ThrowIfNotSupported(options, _adapter.PacketFormatterAdapter.ProtocolVersion);
             }
 
-            ThrowIfDisposed();
-            ThrowIfNotConnected();
-
             var subscribePacket = MqttPacketFactories.Subscribe.Create(options);
             subscribePacket.PacketIdentifier = _packetIdentifierProvider.GetNextPacketIdentifier();