ASP.NET MVC Exception Handling with AJAX/JSON

Question

I have several methods in a controller that look like:

[HttpPost]
public ActionResult AddEditCommentToInvoice(string invoiceNumber, string comments)
{
    var response = new { success = true, msg = "Comment saved", statusMsg = "Comment saved" };

    try
    {
        var recordsModified = invoiceService.AddCommentsToInvoice(invoiceNumber, comments);
        Log.Info(recordsModified ? "Updated Comment" : "Did not update Comment");

    } catch (Exception ex) {
        Response.StatusCode = (int)HttpStatusCode.InternalServerError;
        return Json(new {
            success = false,
            msg = "There is missing field data",
            statusMsg = ex.Message
        }, JsonRequestBehavior.AllowGet);
    }

    return Json(response, JsonRequestBehavior.AllowGet);
}

While this code works, I'm not comfortable with this approach because:

Try/Catches are expensive
The code catches System.Exception
The code is ugly

Now I know that I can use OnException or the HandleError attribute.
I also did some research on ELMAH and this looks promising.

But I still want to return JSON via AJAX to my user to indicate whether the operation was a success or not.

So my question is, has anyone used any of the three methods (or specifically ELMAH) to return JSON via AJAX?

ELMAH only monitors and reports on unhandled exceptions it does not modify your application flow, the attribute approach is your best bet. — KiwiPiet
– KiwiPiet, Commented Dec 2, 2015 at 19:33
I do the same thing and I have always hated it. I look forward to seeing a solution. It was always one of those items on my 'technical debt'. — kryptonkal
– kryptonkal, Commented Dec 2, 2015 at 20:16
@kryptonkal - I just came across this - plainoldstan.blogspot.cz/2012/08/… — coson
– coson, Commented Dec 2, 2015 at 20:43

Brian Mains · Accepted Answer · 2015-12-02 20:48:58Z

2

I use another approach that's an approach that can be applied at the controller level or globally through GlobalFilters. In my MVC controllers, you could override OnActionExecuted method, and do this:

   protected override void OnActionExecuted(ActionExecutedContext filterContext)
   {
      if (filterContext.Exception != null)
      {
         filterContext.Result = Json(new { success = false });
         return;
      }

      base.OnActionExecuted(filterContext);
   }

This could also be done as an action filter attribute. You wouldn't need any exception handling in your controllers - if an exception occurs, then this is handled within the context of the result.

answered Dec 2, 2015 at 20:48

Brian Mains

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