asp.net web api - Exception in HttpControllerDispatcher -

in webapiconfig::register(...) replaced httpcontrollerselector own controller selector. when fire off post request selectcontroller member correctly called , return controllerdescriptor correct type of controller. httpcontrollerdispatcher raising exception saying "the given not present in dictionary." has idea how debug such error?

the complete exception message is:

the given key not present in dictionary.","exceptiontype":"system.collections.generic.keynotfoundexception","stacktrace":"   @ system.collections.generic.dictionary`2.get_item(tkey key)\r\n    @ system.web.http.controllers.apicontrolleractionselector.actionselectorcacheitem.findactionmatchrequiredrouteandqueryparameters(ienumerable`1 candidatesfound)\r\n    @ system.web.http.controllers.apicontrolleractionselector.actionselectorcacheitem.findmatchingactions(httpcontrollercontext controllercontext, boolean ignoreverbs)\r\n    @ system.web.http.controllers.apicontrolleractionselector.actionselectorcacheitem.selectaction(httpcontrollercontext controllercontext)\r\n    @ system.web.http.controllers.apicontrolleractionselector.selectaction(httpcontrollercontext controllercontext)\r\n    @ system.web.http.apicontroller.executeasync(httpcontrollercontext controllercontext, cancellationtoken cancellationtoken)\r\n    @ system.web.http.dispatcher.httpcontrollerdispatcher.<sendasync>d__1.movenext()" 

and here controller selector:

public class namespace_http_controller_selector : ihttpcontrollerselector {     private readonly httpconfiguration _configuration;     private readonly lazy<dictionary<string, httpcontrollerdescriptor>> _controller;      public namespace_http_controller_selector(httpconfiguration config)     {         _configuration = config;         _controller = new lazy<dictionary<string, httpcontrollerdescriptor>>(initialize_controller_dictionary);     }      public httpcontrollerdescriptor selectcontroller(httprequestmessage request)     {         var route_data = request.getroutedata();         if(route_data == null)         {             throw new httpresponseexception(httpstatuscode.notfound);         }          var controller_name = get_controller_name(route_data);         if(controller_name ==  null)         {             throw new httpresponseexception(httpstatuscode.notfound);         }          var name_space = get_version(route_data);         if (name_space == null)         {             throw new httpresponseexception(httpstatuscode.notfound);         }          var controller_key = string.format(cultureinfo.invariantculture, "{0}.{1}", name_space, controller_name);          httpcontrollerdescriptor descriptor;         if(_controller.value.trygetvalue(controller_key, out descriptor))         {             return descriptor;         }          throw new httpresponseexception(httpstatuscode.notfound);     }      public idictionary<string, httpcontrollerdescriptor> getcontrollermapping()     {         return _controller.value;     }       private dictionary<string, httpcontrollerdescriptor> initialize_controller_dictionary()     {         var dictionary = new dictionary<string, httpcontrollerdescriptor>(stringcomparer.ordinalignorecase);          var assemblies_resolver = _configuration.services.getassembliesresolver();         var controller_resolver = _configuration.services.gethttpcontrollertyperesolver();          var controller_types = controller_resolver.getcontrollertypes(assemblies_resolver);          foreach(var ct in controller_types)         {             var segments = ct.namespace.split(type.delimiter);              var controller_name = ct.name.remove(ct.name.length - defaulthttpcontrollerselector.controllersuffix.length);              var controller_key = string.format(cultureinfo.invariantculture, "{0}.{1}", segments[segments.length - 1], controller_name);               if(dictionary.keys.contains(controller_key) == false)             {                 dictionary[controller_key] = new httpcontrollerdescriptor(_configuration, ct.name, ct);             }         }          return dictionary;     }      private t get_route_variable<t>(ihttproutedata route_data, string name)     {         object result;          if(route_data.values.trygetvalue(name, out result))         {             return (t)result;         }          return default(t);     }       private string get_controller_name(ihttproutedata route_data)     {          var subroute = route_data.getsubroutes().firstordefault();          if( subroute == null )         {             return null;         }          var data_token_value = subroute.route.datatokens.first().value;         if(data_token_value == null)         {             return null;         }           var controller_name = ((httpactiondescriptor[])data_token_value).first().controllerdescriptor.controllername.replace("controller", string.empty);           return controller_name;     }      private string get_version(ihttproutedata route_data)     {         var sub_route_data = route_data.getsubroutes().firstordefault();         if(sub_route_data== null)         {             return null;         }          return get_route_variable<string>(sub_route_data, "apiversion");     } } 

this because not setting subroute data in request before returning descriptor.

httpcontrollerdescriptor descriptor; if(_controller.value.trygetvalue(controller_key, out descriptor)) {     var subroutes = route_data.getsubroutes();     ienumerable<ihttproutedata> filteredsubroutes = subroutes.where(attrroutedata =>     {         httpcontrollerdescriptor currentdescriptor = ((httpactiondescriptor[])route_data.route.datatokens["actions"]).first().controllerdescriptor;         return currentdescriptor != null && currentdescriptor.controllername.equals(descriptor.controllername, stringcomparison.ordinalignorecase);     });     route_data.values["ms_subroutes"] = filteredsubroutes.toarray();     return descriptor; } 

take at: versioning asp.net web api 2 media types