Added readme and incorporated feedback from @JanEggers

Attributes/MqttControllerContextAttribute.cs

+using System;
+using MQTTnet.Server;
+
+namespace MQTTnet.AspNetCore.AttributeRouting.Attributes
+{
+    /// <summary>
+    /// When creating a custom controller that does not inherit from <see cref="MqttBaseController"/>, this attribute
+    /// tells the activator which property the <see cref="MqttApplicationMessageInterceptorContext"/> should be assigned to.
+    /// </summary>
+    [AttributeUsage(AttributeTargets.Property, AllowMultiple = false, Inherited = true)]
+    public class MqttControllerContextAttribute : Attribute
+    {
+    }
+}
\ No newline at end of file

Example/MqttControllers/MqttWeatherForecastController.cs

@@ -24,8 +24,8 @@ namespace Example.MqttControllers
             // We have access to the MqttContext
             if (zipCode != 90210) { MqttContext.CloseConnection = true; }
 
-            // We have access to the request context
-            var temperature = BitConverter.ToDouble(Request.Payload);
+            // We have access to the raw message
+            var temperature = BitConverter.ToDouble(Message.Payload);
 
             _logger.LogInformation($"It's {temperature} degrees in Hollywood");
 

Example/Startup.cs

-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Threading.Tasks;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting;
-using Microsoft.AspNetCore.Mvc;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Hosting;
-using Microsoft.Extensions.Logging;
 using MQTTnet.AspNetCore;
 using MQTTnet.AspNetCore.AttributeRouting;
 using MQTTnet.AspNetCore.Extensions;
@@ -30,12 +24,17 @@ namespace Example
             // Configure AspNetCore controllers
             services.AddControllers();
 
-            // Configure MQTT controllers
+            // Identify and build routes for the current assembly
+            services.AddMqttControllers();
+
             services
-                .AddHostedMqttServerWithAttributeRouting(s =>
+                .AddHostedMqttServerWithServices(s =>
                 {
                     // Optionally set server options here
                     s.WithoutDefaultEndpoint();
+
+                    // Enable Attribute routing
+                    s.WithAttributeRouting();
                 })
                 .AddMqttConnectionHandler()
                 .AddConnections();

Extensions/ServiceCollectionExtensions.cs

-using Microsoft.Extensions.DependencyInjection;
-using MQTTnet.AspNetCore.Extensions;
+// Copyright (c) Atlas Lift Tech Inc. All rights reserved.
+
+using Microsoft.Extensions.DependencyInjection;
+using MQTTnet.AspNetCore.AttributeRouting.Routing;
 using MQTTnet.Server;
-using System;
-using System.Diagnostics;
-using System.Linq;
 using System.Reflection;
 
 namespace MQTTnet.AspNetCore.AttributeRouting
 {
     public static class ServiceCollectionExtensions
     {
-        public static IServiceCollection AddHostedMqttServerWithAttributeRouting(this IServiceCollection services, Action<AspNetMqttServerOptionsBuilder> configure)
+        public static IServiceCollection AddMqttControllers(this IServiceCollection services)
         {
-            var assemblies = new Assembly[] { Assembly.GetEntryAssembly() };
-            var routeTable = MqttRouteTableFactory.Create(assemblies);
-
-            services.AddSingleton(routeTable);
-
-            services.AddHostedMqttServerWithServices(options =>
+            services.AddSingleton(c =>
             {
-                configure(options);
-
-                var rt = options.ServiceProvider.GetRequiredService<MqttRouteTable>();
-
-                options.WithApplicationMessageInterceptor(new MqttServerApplicationMessageInterceptorDelegate(context =>
-                        {
-                            var ctx = new MqttRouteContext(context.ApplicationMessage.Topic);
-
-                            rt.Route(ctx);
-
-                            if (ctx.Handler == null)
-                            {
-                                context.AcceptPublish = false;
-                            }
-                            else
-                            {
-                                object result = null;
-                                ParameterInfo[] parameters = ctx.Handler.GetParameters();
+                // future enhancement: scan for other AppParts, if needed
 
-                                using (var scope = options.ServiceProvider.CreateScope())
-                                {
-                                    object classInstance = ActivatorUtilities.GetServiceOrCreateInstance(scope.ServiceProvider, ctx.Handler.DeclaringType);
+                var assemblies = new Assembly[] { Assembly.GetEntryAssembly() };
 
-                                    // TODO: Handle instance where we get a non MqttBaseController for some reason
-                                    ((MqttBaseController)classInstance).MqttContext = context;
+                return MqttRouteTableFactory.Create(assemblies);
+            });
 
-                                    try
-                                    {
-                                        if (parameters.Length == 0)
-                                        {
-                                            result = ctx.Handler.Invoke(classInstance, null);
-                                        }
-                                        else
-                                        {
-                                            // TODO: Better error messages if parameters don't align properly
-                                            object[] paramArray = parameters.Select(p => ctx.Parameters[p.Name]).ToArray();
+            services.AddSingleton<ITypeActivatorCache>(new TypeActivatorCache());
+            services.AddSingleton<MqttRouter>();
 
-                                            result = ctx.Handler.Invoke(classInstance, paramArray);
-                                        }
-                                    }
-                                    catch (Exception ex)
-                                    {
-                                        Debug.WriteLine(ex);
-                                    }
-                                }
+            return services;
+        }
 
-                                context.AcceptPublish = true;
+        public static AspNetMqttServerOptionsBuilder WithAttributeRouting(this AspNetMqttServerOptionsBuilder options)
+        {
+            var router = options.ServiceProvider.GetRequiredService<MqttRouter>();
+            var interceptor = new MqttServerApplicationMessageInterceptorDelegate(context => router.OnIncomingApplicationMessage(options, context));
 
-                                Debug.WriteLine($"Matched route ${context.ApplicationMessage.Topic} to handler ${ctx.Handler.DeclaringType.FullName}.{ctx.Handler.Name}");
-                            }
-                        }));
-            });
+            options.WithApplicationMessageInterceptor(interceptor);
 
-            return services;
+            return options;
         }
     }
 }
\ No newline at end of file

MQTTnet.AspNetCore.AttributeRouting.csproj

@@ -3,22 +3,25 @@
 	<PropertyGroup>
 		<TargetFrameworks>netstandard2.0;netcoreapp3.1</TargetFrameworks>
 		<GeneratePackageOnBuild>true</GeneratePackageOnBuild>
-		<Description>
-			This is a support library to integrate AttributeRouting into MQTTnet with AspNetCore.
+		<Description>This is a support library to integrate AttributeRouting into MQTTnet with AspNetCore.
 
-			Easily create Controllers and Actions to process incoming MQTT messages using a familiar paradigm.  Bring your WebAPI development experience directly into processing MQTT messages.
-		</Description>
-		<Copyright>Copyright (c) Anton Vishnyak 2020</Copyright>
+Easily create Controllers and Actions to process incoming MQTT messages using attribute-based routing against the incoming message topic.</Description>
+		<Copyright>Copyright (c) Atlas Lift Tech Inc. 2020</Copyright>
 		<PackageLicenseExpression>MIT</PackageLicenseExpression>
 		<PackageTags>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 Blazor AspNetCore</PackageTags>
 		<Company>Atlas Lift Tech Inc.</Company>
 		<Authors>Anton Vishnyak</Authors>
-		<AssemblyVersion>0.0.0.0</AssemblyVersion>
-		<FileVersion>0.0.0.0</FileVersion>
+		<AssemblyVersion>0.1.0.0</AssemblyVersion>
+		<FileVersion>0.1.0.0</FileVersion>
 		<SignAssembly>true</SignAssembly>
 		<DelaySign>false</DelaySign>
 		<AssemblyOriginatorKeyFile>codeSigningKey.pfx</AssemblyOriginatorKeyFile>
 		<LangVersion>default</LangVersion>
+		<RepositoryUrl>https://github.com/Atlas-LiftTech/MQTTnet.AspNetCore.AttributeRouting</RepositoryUrl>
+		<RepositoryType>GIT</RepositoryType>
+		<PackageReleaseNotes>Beta release</PackageReleaseNotes>
+		<Version>0.1.0</Version>
+		<PackageRequireLicenseAcceptance>false</PackageRequireLicenseAcceptance>
 	</PropertyGroup>
 
 	<ItemGroup Condition="'$(TargetFramework)' == 'netcoreapp3.1'">

README.md

+<p align="center">
+<img src="https://github.com/chkr1011/MQTTnet/blob/master/Images/icon_det_256.png?raw=true" width="196">
+<br/>
+Attribute Routing
+<br/>
+</p>
+
+[![NuGet Badge](https://buildstats.info/nuget/MQTTnet.AspNetCore.AttributeRouting)](https://www.nuget.org/packages/MQTTnet.AspNetCore.AttributeRouting)
+[![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](https://github.com/Atlas-LiftTech/MQTTnet.AspNetCore.AttributeRouting/LICENSE)
+
+# MQTTnet AspNetCore AttributeRouting
+
+This addon to MQTTnet provides the ability to define controllers and use attribute-based routing against message topics in a manner that is very similar to AspNet Core.
+
+## Features
+
+* Encapsulate your incoming message logic in controllers
+* Use familiar paradigms from AspNetCore in your MQTT logic
+* First-class support for dependency injection using existing ServiceProvider implementaiton in your AspNetCore project
+* Use together with any other MQTTnet options
+
+## Performance Note
+
+This library has not been tested against a very high-load environment yet.  Ensure you do your own load testing prior to use in production.  All performance improvement PRs are welcome.
+
+## Supported frameworks
+
+* .NET Standard 2.0+
+* .NET Core 3.1+
+
+## Supported MQTT versions
+
+* 5.0.0
+* 3.1.1
+* 3.1.0
+
+## Nuget
+
+This library is available as a nuget package: <https://www.nuget.org/packages/MQTTnet.AspNetCore.AttributeRouting/>
+
+## Usage
+
+Install this package and MQTTnet from nuget.
+
+Modify your `Startup.cs` with the following options:
+
+```csharp
+public void ConfigureServices(IServiceCollection services)
+{
+	// ... All your other configuration ...
+
+	// Identify and build routes for the current assembly
+	services.AddMqttControllers();
+
+	services
+		.AddHostedMqttServerWithServices(s =>
+		{
+			// Optionally set server options here
+			s.WithoutDefaultEndpoint();
+
+			// Enable Attribute routing
+			s.WithAttributeRouting();
+		})
+		.AddMqttConnectionHandler()
+		.AddConnections();
+}
+```
+
+Create your controllers by inheriting from MqttBaseController and adding actions to it like so:
+
+```csharp
+[MqttController]
+[MqttRoute("[controller]")] // Optional route prefix
+public class MqttWeatherForecastController : MqttBaseController
+{
+	private readonly ILogger<MqttWeatherForecastController> _logger;
+
+	// Controllers have full support for dependency injection just like AspNetCore controllers
+	public MqttWeatherForecastController(ILogger<MqttWeatherForecastController> logger)
+	{
+		_logger = logger;
+	}
+
+	// Supports template routing with typed constraints just like AspNetCore
+	// Action routes compose together with the route prefix on the controller level
+	[MqttRoute("{zipCode:int}/temperature")]
+	public async Task WeatherReport(int zipCode)
+	{
+		// We have access to the MqttContext
+		if (zipCode != 90210) { MqttContext.CloseConnection = true; }
+
+		// We have access to the raw message
+		var temperature = BitConverter.ToDouble(Message.Payload);
+
+		_logger.LogInformation($"It's {temperature} degrees in Hollywood");
+
+		if (temperature <= 0 && temperature >= 130)
+		{
+			// Example validation
+			MqttContext.AcceptPublish = false;
+		}
+	}
+}
+```
+
+[See a full example project here](https://github.com/Atlas-LiftTech/MQTTnet.AspNetCore.AttributeRouting/tree/master/Example)
+
+
+## Contributions
+
+Contributions are welcome.  Please open an issue to discuss your idea prior to sending a PR.
+
+## MIT License
+
+See https://github.com/Atlas-LiftTech/MQTTnet.AspNetCore.AttributeRouting/LICENSE.

Routing/ITypeActivatorCache.cs

+// Copyright (c) .NET Foundation. All rights reserved. Licensed under the Apache License, Version 2.0. See License.txt
+// in the project root for license information.
+
+using System;
+
+namespace MQTTnet.AspNetCore.AttributeRouting.Routing
+{
+    internal interface ITypeActivatorCache
+    {
+        TInstance CreateInstance<TInstance>(IServiceProvider serviceProvider, Type implementationType);
+    }
+}
\ No newline at end of file

Routing/MqttBaseController.cs

 // Copyright (c) Atlas Lift Tech Inc. All rights reserved.
 
+using MQTTnet.AspNetCore.AttributeRouting.Attributes;
 using MQTTnet.Server;
 
 namespace MQTTnet.AspNetCore.AttributeRouting
@@ -7,8 +8,15 @@ namespace MQTTnet.AspNetCore.AttributeRouting
     [MqttController]
     public abstract class MqttBaseController
     {
+        /// <summary>
+        /// Connection context is set by controller activator. If this class is instantiated directly, it will be null.
+        /// </summary>
+        [MqttControllerContext]
         public MqttApplicationMessageInterceptorContext MqttContext { get; set; }
 
-        public MqttApplicationMessage Request => MqttContext.ApplicationMessage;
+        /// <summary>
+        /// Gets the <see cref="MqttApplicationMessage"/> for the executing action.
+        /// </summary>
+        public MqttApplicationMessage Message => MqttContext.ApplicationMessage;
     }
 }
\ No newline at end of file

Routing/MqttRouteTableFactory.cs

@@ -35,7 +35,7 @@ namespace MQTTnet.AspNetCore.AttributeRouting
             var asm = assemblies ?? new Assembly[] { Assembly.GetExecutingAssembly() };
 
             var actions = asm.SelectMany(a => a.GetTypes())
-                .Where(type => type.IsSubclassOf(typeof(MqttBaseController)))
+                .Where(type => type.GetCustomAttribute(typeof(MqttControllerAttribute), true) != null)
                 .SelectMany(type => type.GetMethods(BindingFlags.Instance | BindingFlags.DeclaredOnly | BindingFlags.Public))
                 .Where(m => !m.GetCustomAttributes(typeof(System.Runtime.CompilerServices.CompilerGeneratedAttribute), true).Any() && !m.IsDefined(typeof(NonActionAttribute)));
 

Routing/MqttRouter.cs

+// Copyright (c) Atlas Lift Tech Inc. All rights reserved.
+
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Logging;
+using MQTTnet.AspNetCore.AttributeRouting.Attributes;
+using MQTTnet.Server;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Reflection;
+
+namespace MQTTnet.AspNetCore.AttributeRouting.Routing
+{
+    internal class MqttRouter
+    {
+        private readonly ILogger<MqttRouter> logger;
+
+        public MqttRouter(ILogger<MqttRouter> logger)
+        {
+            this.logger = logger;
+        }
+
+        internal void OnIncomingApplicationMessage(AspNetMqttServerOptionsBuilder options, MqttApplicationMessageInterceptorContext context)
+        {
+            var routeTable = options.ServiceProvider.GetRequiredService<MqttRouteTable>();
+            var typeActivator = options.ServiceProvider.GetRequiredService<ITypeActivatorCache>();
+            var routeContext = new MqttRouteContext(context.ApplicationMessage.Topic);
+
+            routeTable.Route(routeContext);
+
+            if (routeContext.Handler == null)
+            {
+                // Route not found
+                logger.LogDebug($"Rejecting message publish because '{context.ApplicationMessage.Topic}' did not match any known routes.");
+
+                context.AcceptPublish = false;
+            }
+            else
+            {
+                object result = null;
+
+                using (var scope = options.ServiceProvider.CreateScope())
+                {
+                    var classInstance = typeActivator.CreateInstance<object>(scope.ServiceProvider, routeContext.Handler.DeclaringType);
+
+                    // Potential perf improvement is to cache this reflection work in the future.
+                    var activateProperties = routeContext.Handler.DeclaringType.GetRuntimeProperties()
+                        .Where((property) =>
+                        {
+                            return
+                                property.IsDefined(typeof(MqttControllerContextAttribute)) &&
+                                property.GetIndexParameters().Length == 0 &&
+                                property.SetMethod != null &&
+                                !property.SetMethod.IsStatic;
+                        })
+                        .ToArray();
+
+                    if (activateProperties.Length == 0)
+                    {
+                        logger.LogDebug($"MqttController '{routeContext.Handler.DeclaringType.FullName}' does not have a property that can accept a controller context.  You may want to add a [{nameof(MqttControllerContextAttribute)}] to a pubilc property.");
+                    }
+
+                    foreach (var property in activateProperties)
+                    {
+                        property.SetValue(classInstance, context);
+                    }
+
+                    ParameterInfo[] parameters = routeContext.Handler.GetParameters();
+
+                    if (parameters.Length == 0)
+                    {
+                        result = routeContext.Handler.Invoke(classInstance, null);
+                        context.AcceptPublish = true;
+                    }
+                    else
+                    {
+                        object[] paramArray;
+
+                        try
+                        {
+                            paramArray = parameters.Select(p => MatchParameterOrThrow(p, routeContext.Parameters)).ToArray();
+
+                            result = routeContext.Handler.Invoke(classInstance, paramArray);
+                            context.AcceptPublish = true;
+                        }
+                        catch (ArgumentException ex)
+                        {
+                            logger.LogError(ex, $"Unable to match route parameters to all arguments. See inner exception for details.");
+
+                            context.AcceptPublish = false;
+                        }
+                        catch (Exception ex)
+                        {
+                            logger.LogError(ex, $"Unhandled MQTT action exception. See inner exception for details.");
+
+                            // This is an unandled exception from the invoked action
+                            context.AcceptPublish = false;
+                        }
+                    }
+                }
+            }
+        }
+
+        private static object MatchParameterOrThrow(ParameterInfo param, IReadOnlyDictionary<string, object> availableParmeters)
+        {
+            if (!availableParmeters.TryGetValue(param.Name, out object value))
+            {
+                if (param.IsOptional)
+                {
+                    return null;
+                }
+                else
+                {
+                    throw new ArgumentException($"No matching route parameter for \"{param.ParameterType.Name} {param.Name}\"", param.Name);
+                }
+            }
+
+            if (!param.ParameterType.IsAssignableFrom(value.GetType()))
+            {
+                throw new ArgumentException($"Cannot assign type \"{value.GetType()}\" to parameter \"{param.ParameterType.Name} {param.Name}\"", param.Name);
+            }
+
+            return value;
+        }
+    }
+}
\ No newline at end of file

Routing/TypeActivatorCache.cs

+// Copyright (c) .NET Foundation. All rights reserved. Licensed under the Apache License, Version 2.0. See License.txt
+// in the project root for license information.
+
+// Modifications Copyright (c) Atlas Lift Tech Inc. All rights reserved.
+
+using Microsoft.Extensions.DependencyInjection;
+using System;
+using System.Collections.Concurrent;
+
+namespace MQTTnet.AspNetCore.AttributeRouting.Routing
+{
+    /// <summary>
+    /// Caches <see cref="ObjectFactory"/> instances produced by <see cref="ActivatorUtilities.CreateFactory(Type, Type[])"/>.
+    /// </summary>
+    internal class TypeActivatorCache : ITypeActivatorCache
+    {
+        private readonly Func<Type, ObjectFactory> _createFactory = (type) => ActivatorUtilities.CreateFactory(type, Type.EmptyTypes);
+
+        private readonly ConcurrentDictionary<Type, ObjectFactory> _typeActivatorCache = new ConcurrentDictionary<Type, ObjectFactory>();
+
+        /// <inheritdoc/>
+        public TInstance CreateInstance<TInstance>(IServiceProvider serviceProvider, Type implementationType)
+        {
+            if (serviceProvider == null)
+            {
+                throw new ArgumentNullException(nameof(serviceProvider));
+            }
+
+            if (implementationType == null)
+            {
+                throw new ArgumentNullException(nameof(implementationType));
+            }
+
+            var createFactory = _typeActivatorCache.GetOrAdd(implementationType, _createFactory);
+
+            return (TInstance)createFactory(serviceProvider, arguments: null);
+        }
+    }
+}
\ No newline at end of file