How to add custom HTTP Headers in Asp.Net-MVC

Question

I created a custom handler that looks like follow:

public class SitHandler : DelegatingHandler
{
    protected override async Task<HttpResponseMessage> SendAsync(
        HttpRequestMessage request, CancellationToken cancellationToken)
    {
        Debug.WriteLine("Process request");
        // Call the inner handler.
        var response = await base.SendAsync(request, cancellationToken);
        Debug.WriteLine("Process response");
        return response;
    }
}

and registered in the class WebApiConfig:

public static class WebApiConfig
{
    public static void Register(HttpConfiguration config)
    {
      // Web API configuration and services

      //Delegating Handlers
      config.MessageHandlers.Add(new SitHandler());

      // Web API routes
      config.MapHttpAttributeRoutes();

      /*config.Routes.MapHttpRoute(
          name: "DefaultApi",
          routeTemplate: "api/{controller}/{id}",
          defaults: new { id = RouteParameter.Optional }
      );*/
    }
}

and have following route:

[RoutePrefix("")]
public class SignInController : Controller
{
    [Route("", Name = "Default")]
    public ActionResult Index()
    {
      return View();
    }
}

Now when I start the server it show me the correct page as expected:

But the request does not goi throught the handler, why?
And what is an innerhandler?

// Call the inner handler.
var response = await base.SendAsync(request, cancellationToken);

You are mixing up MVC and Web API. You are adding your delegate handler to the WebApi pipeline while your controller is from MVC as it inherits from Controller and not ApiController. What version of api.net-mvc are your using? — Nkosi
– Nkosi, Commented May 24, 2016 at 13:35
You should clarify what your intentions are first. That way others can provide you with answers relevant with what you are trying to do. — Nkosi
– Nkosi, Commented May 24, 2016 at 13:40

Nkosi · Accepted Answer · 2016-05-26 12:52:44Z

6

For MVC you will need to add an ActionFilterAttribute

[AttributeUsage(AttributeTargets.Method | AttributeTargets.Class, AllowMultiple = false, Inherited = true)]
public class MyCustomFilter : System.Web.Mvc.ActionFilterAttribute {
    public override void OnActionExecuted(ActionExecutedContext context) {
        Debug.WriteLine("Process response");
        //From here you have access to the response to process what you need
        //eg: context.HttpContext.Response.Headers.Add("MyCustomHeaderName","value");

        base.OnActionExecuted(context);
    }
}

you can then either use you attribute on an action...

[MyCustomFilter]
[Route("", Name = "Default")]
public ActionResult Index(){...}

, class...

[MyCustomFilter]
[RoutePrefix("")]
public class SignInController : Controller {...}

, or set it globally...

public class FilterConfig {
    public static void RegisterGlobalFilters(GlobalFilterCollection filters) {
        filters.Add(new MyCustomFilter());
    }
}

edited May 26, 2016 at 12:52

answered May 24, 2016 at 14:04

Nkosi

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3 Comments

softshipper Over a year ago

First of all thanks so much for reponse, but it does not work. I used the attribute as class and it does not go through filter. Then I try to register in the FilterConfig class, it throws an exception Exception thrown: 'System.InvalidOperationException' in System.Web.Mvc.dll. I've forgot to mention, that I am using Web MVC and Web API in the project.

softshipper Over a year ago

Do you mean System.Web.Mvc.ActionFilterAttribute? I tried it and it works but I could not find Response.Headers.Add.

Nkosi Over a year ago

Yes that is what i meant. I mixed up filter for web api and mvc. that was a mistake on my part. I've updated the answer with the correct types.

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