Get SessionID via WebMethod from VB.NET to JavaScript

Question

I'm a little clueless having the following code just not working:

Code-behind:

<WebMethod(EnableSession:=True)>
Public Shared Function GetSessionID() As String
    Dim sID = HttpContext.Current.Session.SessionID
    Debug.WriteLine(sID)
    Return sID
End Function

JavaScript:

var sID;

function init() {
    sID = PageMethods.GetSessionID();
...

The sID is obviously there and shown in debug output but in JavaScript sID holds "undefined" because the function returns "undefined" when executed in Firebug console. What's going on there?

Answer 1

You need to define the OnSuccess callback of your PageMethods like this:

var sID;

function init() {
    PageMethods.GetSessionID(OnSuccess);
}

function OnSuccess(response, userContext, methodName) {
    sID = response;
    alert(sID);
}

References:

• Exposing Web Services to Client Script
• Calling Web Services from Client Script

Answer 2

Your code looks OK. Where are you calling the function from? Try defining the variable inside the function:

function init() {
    var sID = PageMethods.GetSessionID();
}

---

If you are trying to read the sessionID why not just read directly from the cookie?

JavaScript

function readCookie(name) {
  var nameEQ = escape(name) + '=',
    ca = document.cookie.split(';'),
    i = 0,
    c;
  for (i = 0; i < ca.length; i++) {
    c = ca[i];
    while (c.charAt(0) === ' ') { c = c.substring(1, c.length); }
    if (c.indexOf(nameEQ) === 0) { return unescape(c.substring(nameEQ.length, c.length)); }
  }
  return null;
}

var sID = readCookie('ASP.NET_SessionId');