jQuery Ajax多用户请求

I am very new into ajax and i am having a strange problem, I have created an asp.net website that have a web service within the project I am calling this web service by following ajax code:

    $.ajax({
    type: "POST",
    url: pageUrl + "/PassData",
    data: JSON.stringify({ aos_code: code }),
    contentType: "application/json; charset=utf-8",
    dataType: "json",
    success: OnSuccessCall
}); 

the c# code is not very complicated, basically it will get the code and call the stored procedure and return some value:

[WebMethod(EnableSession = true)]
public string[] PassData(string aos_code)
{
    // calling the database and returning some data
    return data;
} 

And it works fine; the problem is that if two different users accessing the application in the two different computers and let say they clicking a button at the same time to call the server side function via Ajax, it will return the “500 internal server error”.

I am not sure how exactly Ajax work, is request are belong to same session or all user requesting a single function? Hope it makes sense, and I would really do appreciate for the clarification and help.

Regards,

Error 500 indicates that something went wrong on the server side. Check your console (firebug or similar) to see what exactly happened and try to fix it. Ajax has nothing to do with it, it is simply as if two users visited the same page at the same time.