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

Answer 2

This is not specific to this question but you can check a few things to get better understanding of what is causing the issue.

• Check the status code and type of request in the General section of Request Headers.
• Check the Response Headers if there is any json error.
• Check the Response to get the message, stacktrace and exception type.
• Check the Request Payload section in Headers for parameters passed.

Check this post for more detail.

Answer 3

First, it the webmethod is in the page class, and not in a Webservice class, then it should be static.

Second, the data transfered is not really a string, but an object, so change it to:

var dataString = { 'value':  value  };

Third thing, "type" is for older versions of jquery, you should either change your ajax call to:

method: "GET",
url: pagePath,
data: dataString,
contentType: "application/json; charset=utf-8",
dataType: "json",...

Or change the function in the server side to get post calls, by removing the

UseHttpGet = true

Answer 4

Probably you need to add static to your method declaration as below

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

if this isn't the case, you could F12 the browser->network then click on the error message to see it briefly.

Concerning the reported issue,the problem with get request, try to make it post

Answer 5

The Answer is here :link

the problem is with the annotation I was using the [ScriptMethod(UseHttpGet = true)] which causing the error. just change the value from true to false.