Invalid JSON issue with asp.net jquery ajax call - asp.net

Question

Invalid JSON issue with asp.net jquery ajax call
Hi,
I am facing a strange issue while receiving response for an ajax call when I fire it to page.
I am using jquery to post data to the code behind
Javascript -
var jsonData = { "a": JSON.stringify(obj1),"b": JSON.stringify(obj2)};
jsonData = JSON.stringify(jsonData);
$.ajax({
type: "POST",
contentType: "application/json; charset=utf-8",
url: 'Page.aspx/AjaxCall',
async: true, cache: true, data: jsonData, dataType: "json",
success: function (msg) {
alert('hurray! Success. ' + msg.d);
},
error: function (xhr, textstatus, errorThrown) {
alert('there was an error' + errorThrown);
}
});
C#
[WebMethod]
public static string AjaxCall(string a, string b)
{
Dictionary<object, Dictionary<string, object>> x = new Dictionary<object, Dictionary<string, object>>();
Dictionary<string, object> z = new Dictionary<string, object>();
Dictionary<object, object> y = new Dictionary<object, object>();
int u = 0;
int v = 0;
// deserialise z class
try
{
if (!string.IsNullOrEmpty(b))
{
z = (Dictionary<string, object>)new JavaScriptSerializer().Deserialize(b, typeof(Dictionary<string, object>));
if (z.ContainsKey("IsProctored"))
y.Add("BlurCount", z["BlurCount"]);
if (z.ContainsKey("IsCrossClicked"))
{
y.Add("IsCrossClicked", z["IsCrossClicked"]);
}
}
}
catch (InvalidOperationException ioe)
{
throw new Exception();
}
// deserialise items class
try
{
x = (Dictionary<object, Dictionary<string, object>>)
new JavaScriptSerializer().Deserialize(a, typeof(Dictionary<object, Dictionary<string, object>>));
}
catch (InvalidOperationException ioe)
{
throw new Exception();
}
if (u == 0)
{
throw new Exception();
}
if (v == 0)
{
throw new Exception();
}
if (x.Count == 0)
{
//throw new Exception();
}
try
{
// saves the data in backend
SaveResponse(u, v, x, y);
}
catch (Exception ex)
{
throw new Exception();
}
return "response fired";
}
The error that I get is 'Invalid JSON' (in Firebug's response tab of ajax call). Although it's straightforward ajax call.
I am kinda confused why this maay be happening because this it works on majority of the cases and fails on some other.
Any idea would be a great help.
thanks!

Answer 1

You have lots of throw Exception statements in there.
Any of those would trigger the invalid Json response!
You need to trap error messages and instead of throwing an exception, return some valid Json to indicate the problem.
Also for debugging I suggest using Firefox with HttpFox installed - you can then analyze the exact content of any responses, whether by Ajax or not. I find it an invaluable and free tool for situations like this.

Answer 2

It was because of some strange issue with Firefox 3.6. I restarted the browser and tested it again and things were working as expected.