ASP.NET MVC JsonResult return 500

Question

I have this controller method:

public JsonResult List(int number) {
 var list = new Dictionary <int, string> ();

 list.Add(1, "one");
 list.Add(2, "two");
 list.Add(3, "three");

 var q = (from h in list where h.Key == number select new {
  key = h.Key,
   value = h.Value
 });

 return Json(list);
}

On the client side, have this jQuery script:

$("#radio1").click(function() {
  $.ajax({
    url: "/Home/List",
    dataType: "json",
    data: {
      number: '1'
    },
    success: function(data) {
      alert(data)
    },
    error: function(xhr) {
      alert(xhr.status)
    }
  });
});

I always get an error code 500. What's the problem?

Thank you

Answer 1

If you saw the actual response, it would probably say

This request has been blocked because sensitive information could be disclosed to third party web sites when this is used in a GET request. To allow GET requests, set JsonRequestBehavior to AllowGet.

You'll need to use the overloaded Json constructor to include a JsonRequestBehavior of JsonRequestBehavior.AllowGet such as:

return Json(list, JsonRequestBehavior.AllowGet);

Here's how it looks in your example code (note this also changes your ints to strings or else you'd get another error).

public JsonResult List(int number) {
  var list = new Dictionary<string, string>();

  list.Add("1", "one");
  list.Add("2", "two");
  list.Add("3", "three");

  var q = (from h in list
           where h.Key == number.ToString()
           select new {
             key = h.Key,
             value = h.Value
           });

  return Json(list, JsonRequestBehavior.AllowGet);
}