How to return HttpResponseException with error specificaton (invalid username or invalid password) to the frontend?

Question

How do i return Bad Request exception with text like "Invalid username" to frontend in ApiController. My code:

public class FrontEndController : ApiController
    {
        public string Test(string value)
        {
            if(!isValid(value))
               //how do i throw exception with its code (400 in this case) and message ("Invalid username")
        }
    }

Answer 1

You can change your method return type to HttpResponseMessage and use the built in API functionality to return the error message you'd like.

public class FrontEndController : ApiController
    {
        public HttpResponseMessage Test(string value)
        {
            if(!isValid(value))
              {
                 //Generate error response here
                 return Request.CreateErrorResponse(HttpStatusCode.BadRequest, "Invalid Username");
              }
        }
    }