What to return from ASP.NET MVC action to allow jQuery ajax success event to fire?

I believe the problem is that you're not returning anything in the JsonResult. Try:

return this.Json(string.Empty);

and see if that works. I think that the problem is that you're returning nothing to the jQuery call rather than an empty JSON set:

{}

Returning an empty result may also be useful

return new EmptyResult();

Note: Your return type doesn't need to be ActionResult or event anything that inherits from it. In fact mvc will let you call any public method. However you should always use the most explicit return type you want just like any other method (like JsonResult).

2 quick notes for anyone landing here struggling to trigger the ajax jQuery success callback from an MVC controller:

1. If you're using type: "GET" in your Ajax, you'll need to include JsonRequestBehavior.AllowGet to bypass the default anti JSON Hijacking security measures

 return Json(true, JsonRequestBehavior.AllowGet);

2. As per above, if you've indicated dataType: 'json' in the Ajax request, if you are making a one-way call (e.g. Save) where you don't need anything back, you can return just about anything serializable as Json from the controller. But with a 200, something must be returned. Use a 204 if no data is returned.

Wrong - Triggers the Ajax error handler !

 // Nope - Status 200 must have some content
 return new HttpStatusCodeResult(HttpStatusCode.OK);

 // Also returns a 200 with no data - not allowed
 return new EmptyResult();

Works - triggers the Ajax success handler:

 // Return a 204 if there's no data
 return new HttpStatusCodeResult(HttpStatusCode.NoContent);

 // Return something with a 200 return
 return Json(new {Success = true});