Show exception message to client side

Question

In my asp.net mvc application, I would like to show the user the error message that was used to throw an exception. The exception occurs in an ajax request. I have tried this:

Answer 1

You can create a basecontroller and override the OnException method

public class BaseController : Controller
{
    protected override void OnException(ExceptionContext filterContext)
    {
        //your existing code to log errors here

        filterContext.ExceptionHandled = true;
        if (filterContext.HttpContext.Request.Headers["X-Requested-With"]
                                                                 == "XMLHttpRequest")
        {

            filterContext.Result = new JsonResult
            {
                JsonRequestBehavior = JsonRequestBehavior.AllowGet,
                Data = new
                {
                    Error = true,
                    Message = filterContext.Exception.Message
                }
            };
            filterContext.HttpContext.Response.StatusCode = 500;
            filterContext.ExceptionHandled = true;
        }
        else
        {
            filterContext.Result = new RedirectToRouteResult(new RouteValueDictionary
                {{"controller", "Error"}, {"action", "Index"}});
        }
    }
}

and have all your controllers inherit from this

public class HomeController : BaseController
{

}

So any time an exception happens in your controllers, this OnException method will be executed and if it is an ajax request, It returns a json response with the below structure

{
  Error : true,
  Message : "The message from the exception caught"
}

and now in your javascript, wire up the global ajaxError event and you can read the response coming from server and parse it to a js object and then read the Message property

$(document).ready(function() {

    $(document).ajaxError(function (event, request, settings) {           
        var d = JSON.parse(request.responseText);
        alert("Ajax error:"+d.Message);               
    });

});