Improve connection disposal.

Source/MQTTnet.AspnetCore/ApplicationBuilderExtensions.cs

@@ -28,7 +28,7 @@ namespace MQTTnet.AspNetCore
                 }
 
                 var adapter = app.ApplicationServices.GetRequiredService<MqttWebSocketServerAdapter>();
-                using (var webSocket = await context.WebSockets.AcceptWebSocketAsync(subProtocol))
+                using (var webSocket = await context.WebSockets.AcceptWebSocketAsync(subProtocol).ConfigureAwait(false))
                 {
                     await adapter.RunWebSocketConnectionAsync(webSocket, context);
                 }

Source/MQTTnet.AspnetCore/MqttConnectionContext.cs

@@ -24,8 +24,7 @@ namespace MQTTnet.AspNetCore
                 _input = Connection.Transport.Input;
                 _output = Connection.Transport.Output;
             }
-
-
+            
             _reader = new SpanBasedMqttPacketBodyReader();
         }
 
@@ -33,9 +32,10 @@ namespace MQTTnet.AspNetCore
         private PipeWriter _output;
         private readonly SpanBasedMqttPacketBodyReader _reader;
 
-        public string Endpoint 
+        public string Endpoint
         {
-            get {
+            get
+            {
                 var connection = Http?.HttpContext?.Connection;
                 if (connection == null)
                 {
@@ -53,12 +53,12 @@ namespace MQTTnet.AspNetCore
         public ConnectionContext Connection { get; }
         public MqttPacketFormatterAdapter PacketFormatterAdapter { get; }
 
-        public long BytesSent { get; set; } 
+        public long BytesSent { get; set; }
         public long BytesReceived { get; set; }
 
         public Action ReadingPacketStartedCallback { get; set; }
         public Action ReadingPacketCompletedCallback { get; set; }
-        
+
         private readonly SemaphoreSlim _writerSemaphore = new SemaphoreSlim(1, 1);
 
         public async Task ConnectAsync(TimeSpan timeout, CancellationToken cancellationToken)
@@ -145,7 +145,7 @@ namespace MQTTnet.AspNetCore
         public async Task SendPacketAsync(MqttBasePacket packet, TimeSpan timeout, CancellationToken cancellationToken)
         {
             var formatter = PacketFormatterAdapter;
-           
+
 
             await _writerSemaphore.WaitAsync(cancellationToken).ConfigureAwait(false);
             try

Source/MQTTnet.AspnetCore/MqttConnectionHandler.cs

@@ -10,7 +10,7 @@ namespace MQTTnet.AspNetCore
 {
     public class MqttConnectionHandler : ConnectionHandler, IMqttServerAdapter
     {
-        public Action<MqttServerAdapterClientAcceptedEventArgs> ClientAcceptedHandler { get; set; }
+        public Func<IMqttChannelAdapter, Task> ClientHandler { get; set; }
 
         public override async Task OnConnectedAsync(ConnectionContext connection)
         {
@@ -25,10 +25,11 @@ namespace MQTTnet.AspNetCore
             var formatter = new MqttPacketFormatterAdapter(writer);
             using (var adapter = new MqttConnectionContext(formatter, connection))
             {
-                var args = new MqttServerAdapterClientAcceptedEventArgs(adapter);
-                ClientAcceptedHandler?.Invoke(args);
-
-                await args.SessionTask.ConfigureAwait(false);
+                var clientHandler = ClientHandler;
+                if (clientHandler != null)
+                {
+                    await clientHandler(adapter).ConfigureAwait(false);
+                }
             }
         }
 

Source/MQTTnet.AspnetCore/MqttWebSocketServerAdapter.cs

@@ -21,7 +21,7 @@ namespace MQTTnet.AspNetCore
             _logger = logger.CreateChildLogger(nameof(MqttTcpServerAdapter));
         }
 
-        public Action<MqttServerAdapterClientAcceptedEventArgs> ClientAcceptedHandler { get; set; }
+        public Func<IMqttChannelAdapter, Task> ClientHandler { get; set; }
 
         public Task StartAsync(IMqttServerOptions options)
         {
@@ -43,17 +43,16 @@ namespace MQTTnet.AspNetCore
             var isSecureConnection = clientCertificate != null;
             clientCertificate?.Dispose();
 
-            var writer = new SpanBasedMqttPacketWriter();
-            var formatter = new MqttPacketFormatterAdapter(writer);
-            var channel = new MqttWebSocketChannel(webSocket, endpoint, isSecureConnection);
-            var channelAdapter = new MqttChannelAdapter(channel, formatter, _logger.CreateChildLogger(nameof(MqttWebSocketServerAdapter)));
-
-            var eventArgs = new MqttServerAdapterClientAcceptedEventArgs(channelAdapter);
-            ClientAcceptedHandler?.Invoke(eventArgs);
-
-            if (eventArgs.SessionTask != null)
+            var clientHandler = ClientHandler;
+            if (clientHandler != null)
             {
-                await eventArgs.SessionTask.ConfigureAwait(false);
+                var writer = new SpanBasedMqttPacketWriter();
+                var formatter = new MqttPacketFormatterAdapter(writer);
+                var channel = new MqttWebSocketChannel(webSocket, endpoint, isSecureConnection);
+                using (var channelAdapter = new MqttChannelAdapter(channel, formatter, _logger.CreateChildLogger(nameof(MqttWebSocketServerAdapter))))
+                {
+                    await clientHandler(channelAdapter).ConfigureAwait(false);
+                }   
             }
         }
 

Source/MQTTnet.AspnetCore/TopicFilterBuilder.cs

@@ -0,0 +1,51 @@
+using MQTTnet.Exceptions;
+using MQTTnet.Protocol;
+
+namespace MQTTnet
+{
+    public class TopicFilterBuilder
+    {
+        private MqttQualityOfServiceLevel _qualityOfServiceLevel = MqttQualityOfServiceLevel.AtMostOnce;
+        private string _topic;
+
+        public TopicFilterBuilder WithTopic(string topic)
+        {
+            _topic = topic;
+            return this;
+        }
+
+        public TopicFilterBuilder WithQualityOfServiceLevel(MqttQualityOfServiceLevel qualityOfServiceLevel)
+        {
+            _qualityOfServiceLevel = qualityOfServiceLevel;
+            return this;
+        }
+
+        public TopicFilterBuilder WithAtLeastOnceQoS()
+        {
+            _qualityOfServiceLevel = MqttQualityOfServiceLevel.AtLeastOnce;
+            return this;
+        }
+
+        public TopicFilterBuilder WithAtMostOnceQoS()
+        {
+            _qualityOfServiceLevel = MqttQualityOfServiceLevel.AtMostOnce;
+            return this;
+        }
+
+        public TopicFilterBuilder WithExactlyOnceQoS()
+        {
+            _qualityOfServiceLevel = MqttQualityOfServiceLevel.ExactlyOnce;
+            return this;
+        }
+
+        public TopicFilter Build()
+        {
+            if (string.IsNullOrEmpty(_topic))
+            {
+                throw new MqttProtocolViolationException("Topic is not set.");
+            }
+
+            return new TopicFilter { Topic = _topic, QualityOfServiceLevel = _qualityOfServiceLevel };
+        }
+    }
+}