Accessing current controller executing in DelegatingHandler - asp.net

Question

I was wondering if it's possible to access the controller being executed (or about to be executed) in the SendAsync method of the DelegatingHandler? I can't seem to figure out how to get access to it, and I figure it's because it executes outside of the controller execution...
Is it possible to refer to it?

Answer 1

No, because message handlers operate on raw HttpRequestMessage or raw HttpResponseMessage (in case of continuations). So really, there is no concept of "current controller executing" with DelegatingHandlers since message handlers will be called before dispatching the request to the controller or (again, in the case of continuations) after the controller returns the reponse.
However, it really depends what you are trying to do.
If you want to know to which controller the request will end up getting routed, you can manually call the mechanism that would internally select the controllers.
public class MyHandler : DelegatingHandler
{
protected override System.Threading.Tasks.Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, System.Threading.CancellationToken cancellationToken)
{
var config = GlobalConfiguration.Configuration;
var controllerSelector = new DefaultHttpControllerSelector(config);
// descriptor here will contain information about the controller to which the request will be routed. If it's null (i.e. controller not found), it will throw an exception
var descriptor = controllerSelector.SelectController(request);
// continue
return base.SendAsync(request, cancellationToken);
}
}

Answer 2

Extending the #GalacticBoy solution, it would be better to use
public class MyHandler : DelegatingHandler
{
private static IHttpControllerSelector _controllerSelector = null;
protected override System.Threading.Tasks.Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, System.Threading.CancellationToken cancellationToken)
{
if (_controllerSelector == null)
{
var config = request.GetConfiguration();
_controllerSelector = config.Services.GetService(typeof(IHttpControllerSelector)) as IHttpControllerSelector;
}
try
{
// descriptor here will contain information about the controller to which the request will be routed. If it's null (i.e. controller not found), it will throw an exception
var descriptor = _controllerSelector.SelectController(request);
}
catch
{
// controller not found
}
// continue
return base.SendAsync(request, cancellationToken);
}
}

Answer 3

Depending on what your doing with the information maybe your fine with getting the information after the request is executed. For example logging the executed controller/action.
using System;
using System.Net.Http;
using System.Threading;
using System.Threading.Tasks;
using System.Web;
namespace Example
{
public class SampleHandler : DelegatingHandler
{
protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
{
return base.SendAsync(request, cancellationToken)
.ContinueWith(task =>
{
HttpResponseMessage response = task.Result;
string actionName = request.GetActionDescriptor().ActionName;
string controllerName = request.GetActionDescriptor().ControllerDescriptor.ControllerName;
// log action/controller or do something else
return response;
}, cancellationToken);
}
}
}