Custom WebApi routing not working

Question

I am trying to create a custom route for a web api controller:

[System.Web.Http.RoutePrefix("api/admin")]
public class AdminApiController : BaseApiController
{
    [Route("~/echo")]
    public string Echo()
    {
        return "Hello World";
    }
}

I expect to go to http://example.com/api/admin/echo and receive 'Hello world' but in stead I get an error:

<Error>
    <Message>
        No HTTP resource was found that matches the request URI 'http://example.com/api/admin/echo'.
    </Message>
    <MessageDetail>
    No type was found that matches the controller named 'admin'.
    </MessageDetail>
</Error>

Answer 1

Replace the tilde (~)

A tilde (~) on the method attribute overrides the route prefix of the controller:

[RoutePrefix("api/admin")]
public class AdminApiController : BaseApiController {
    // GET /api/admin/echo
    [HttpGet]
    [Route("echo")] 
    public string Echo() {
        return "Hello World";
    }
    // GET /echo
    [HttpGet]
    [Route("~/echo")]
    public string Echo2() {
        return "Hello World 2";
    }
}

Just to be safe you also need to make sure that you Enable Attribute Routing

To enable attribute routing, call MapHttpAttributeRoutes during configuration. This extension method is defined in the System.Web.Http.HttpConfigurationExtensions class.

public static class WebApiConfig {
    public static void Register(HttpConfiguration config) {
        // Attribute routing.
        config.MapHttpAttributeRoutes();

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