Attribute routing not working when controller is loaded dynamically (using custom controller selector)RSS

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  dtf017

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  Attribute routing not working when controller is loaded dynamically (using custom controller sele...

  Oct 17, 2019 04:41 PM|dtf017|LINK

  I'm creating a selfhost REST server that dynamically loads controllers.
  When my controller is defined in my server project, then attribute routing works fine.
  When same controller is dynamically loaded then it seems attribute routing is not working.

  Here is what i do:
  I'm creating a self hosted REST server (using Owin):

  string baseUri = string.Concat("http://+:12345/MyServer");
  myserver = WebApp.Start<Startup>(baseUri);
  Console.WriteLine("MyServer is listening at " + baseUri);
  ...

  I create a static controller just to make sure it works ok with my settings:

  public class SampleController : ApiController
  {
      public SampleController() { }
  
      [HttpGet]
      [Route("api/Sample/Test")]
      [Route("api/Sample/Test/{data}")]
      [ActionName("Test")]
      public string GetTest(string data)
      {
          return Test(data);
      }
  
      [HttpPost]
      [Route("api/Sample/Test")]
      public string Test([FromBody] string data)
      {
          return string.Concat("Test - Received ", data);
      }
  ...

  My startup class looks like this:

  public class Startup
  {
      public void Configuration(IAppBuilder app)
      {
          var webApiConfiguration = ConfigureWebApi();
          app.UseWebApi(webApiConfiguration);
      }
  
      private HttpConfiguration ConfigureWebApi()
      {
          HttpConfiguration config = new HttpConfiguration();
          config.MapHttpAttributeRoutes();
  
          config.Routes.MapHttpRoute(
                      "DefaultApi",
                      "api/{controller}/{action}/{id}",
                      new { id = RouteParameter.Optional});
  
          DynControllerSelector custom = new DynControllerSelector(config);
  
          config.Services.Replace(typeof(IHttpControllerSelector), custom);
  
          return config;
      }
  }

  Then i dynamically load another controller which has the same methods and definition exposed than the static one. To do that i use a custom controller selector:

  public DynControllerSelector(HttpConfiguration configuration) : base(configuration)
   {
      _Configuration = configuration;
      _ControlleDescriptorDict = new ConcurrentDictionary<string, HttpControllerDescriptor>();
   }
   public override HttpControllerDescriptor SelectController(HttpRequestMessage request)
   {
      HttpControllerDescriptor httpControllerDesc = null;
      try
      {
        IDictionary<string, HttpControllerDescriptor> controllers = GetControllerMapping();
        //string controllerName = base.GetControllerName(request); // is null for some reason
       // Just get the controler in a hack way for now
      string controllerName = request.RequestUri.LocalPath.Replace("/MyServer/api/", "");
      int idx = controllerName.IndexOf("/");
      controllerName = controllerName.Substring(0, idx);
  
      if (!controllers.ContainsKey(controllerName))
      {
         if (_ControlleDescriptorDict.TryGetValue(controllerName, out httpControllerDesc) == false)
         {
          lock (_mlock)
          {
              if (_ControlleDescriptorDict.TryGetValue(controllerName, out httpControllerDesc) == false) // Check that controller has not been created while we were waiting for the lock
              {
                string assemblyName = string.Concat(controllerName, ".dll");
                if (System.IO.File.Exists(assemblyName))
                {
                   Assembly assembly = Assembly.LoadFrom(assemblyName);
                   var types = assembly.GetTypes();
                   var matchedTypes = types.Where(i => typeof(IHttpController).IsAssignableFrom(i)).ToList();
                   var matchedController = matchedTypes.FirstOrDefault(i => i.Name.ToLower() == controllerName.ToLower() + "controller");
                   if (matchedController == null) throw new Exception(string.Concat("Failed to find controller ", controllerName, "Controller"));
                   httpControllerDesc = new HttpControllerDescriptor(_Configuration, controllerName, matchedController);
  
                  _ControlleDescriptorDict.TryAdd(controllerName, httpControllerDesc);
                 }
                 else
                 {
                  throw new Exception(string.Concat("Failed to load assembly ", assemblyName));
                  }
               }
            }
           }
        }
           else
              httpControllerDesc = base.SelectController(request);
  . . 

  They should both use the same routing settings.

  I can call (HTTP GET) my static controller using attribute routing: http://localhost:12345/MyServer/api/Sample/Test/hello2 
  That works fine.

  Problem is when i try the same thing on my dynamic controller: http://localhost:12345/MyServer/api/MyDynamic/Test/hello2 

  I get following error: { "Message": "The requested resource does not support http method 'GET'." }

  It seems somehow the attribute routing is not enabled for my dynamic controller.
  If i use query parameters, it works just fine: http://localhost:12345/MyServer/api/MyDynamic/Test?data=hello

  How can i make it work?

  Thanks in advance for your help

  Nick

• • Reply
  bruce (sqlwo...

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  Re: Attribute routing not working when controller is loaded dynamically (using custom controller...

  Oct 17, 2019 06:45 PM|bruce (sqlwork.com)|LINK

  Attribute routing runs at startup. It uses reflection on all loaded modules to build the route table. As you are loading controllers after this step, they are not “seen”. You need to go thru the attribute routing source code for the version you are using and see if there is a way to trigger a reload of the route table. 
  
  

  bruce (sqlwork.com)
• • Reply
  dtf017

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  Re: Attribute routing not working when controller is loaded dynamically (using custom controller...

  Oct 21, 2019 07:19 AM|dtf017|LINK

  Hi Bruce,

  Thanks for your response. I figured that out but question is how to set the routing after the controller has been loaded.

  Also this should not impact other controller already dynamically loaded.

  That is the part i'm missing. Still thanks for your response.

• • Reply
  Fei Han - MS...

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  Re: Attribute routing not working when controller is loaded dynamically (using custom controller...

  Oct 24, 2019 03:19 AM|Fei Han - MSFT|LINK

  Hi dtf017,

  To make dynamically loaded controller work with attribute routing, you can try to implement custom IAssembliesResolver like below.

  public class MyAssembliesResolver : DefaultAssembliesResolver
  {
      public override ICollection<Assembly> GetAssemblies()
      {
          ICollection<Assembly> baseAssemblies = base.GetAssemblies();
          List<Assembly> assemblies = new List<Assembly>(baseAssemblies);
  
          string thirdPartySource = @"D:\DynamicAPIsController\APIs\";
  
          if (!string.IsNullOrWhiteSpace(thirdPartySource))
          {
              if (Directory.Exists(thirdPartySource))
              {
                  foreach (var file in Directory.GetFiles(thirdPartySource, "*.*", SearchOption.AllDirectories))
                  {
                      if (Path.GetExtension(file) == ".dll")
                      {
                          var externalAssembly = Assembly.LoadFrom(file);
  
                          baseAssemblies.Add(externalAssembly);
                      }
                  }
              }
          }
          return baseAssemblies;
      }
  }

  In Startup.cs

  //...
  
  config.Services.Replace(typeof(IAssembliesResolver), new MyAssembliesResolver());
  config.MapHttpAttributeRoutes();
  
  //...

  Test Result

  

  With Regards,

  Fei Han

  
  MSDN Community Support
  Please remember to "Mark as Answer" the responses that resolved your issue.