ASP.NET 500 Internal Server Error while calling webmethod from javascript

Question

I\'m trying to call the webmethod fucntionality using AJAX but unable to get the appropriate results. I have googled my problem and found many solution but thos

Answer 1

In my case the problem was the "data" field (both cases, GET and POST). As a test, remove the "data" from the AJAX call and also remove the web method parameter, if it works, then the problem is the format of the "data" field:

$.ajax({
   type: "GET",
   url: pagePath,
   contentType: "application/json; charset=utf-8",
   dataType: "json",
   ...

[WebMethod]
[ScriptMethod(UseHttpGet = true)]
public string getUsername()
{
    return "True";
}

Some examples:

data: JSON.stringify({ "parameter": variable })     WORKS
data: JSON.stringify({ parameter: variable })       WORKS
data: '{"parameter": "' + variable + '"}'           WORKS
data: '{parameter: ' + variable + '}'               don't works 
data: JSON.stringify({ 'parameter': 'value' })      WORKS
data: '{"parameter":"value"}'                       WORKS
data: "{'parameter':'value'}"                       WORKS
data: '{parameter:value}'                           don't works
data: {parameter:value}                             don't works
data: {"parameter":"value"}                         don't works
data: {'parameter':'value'}                         don't works