How to code ASP.NET WebMethod for Ajax Call

Question

What the heck am I doing wrong here?

I get this error: [ArgumentException: Unknown web method Test2. Parameter name: methodName] System.Web.Script.Services.WebServiceData.GetMethodData(String methodName) +540418 System.Web.Handlers.ScriptModule.OnPostAcquireRequestState(Object sender, EventArgs eventArgs) +213 System.Web.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +148 System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +75

<script type="text/javascript" src="/Library/JS/jquery-1.7.1.min.js"></script>
<script type="text/javascript">
    $(document).ready(function () {
        setTimeout(function () {  

            $.ajax({
                type: "POST",
                url: "_debug.aspx/Test2",
                data: "{ param: 555 }",
                contentType: "application/json; charset=utf-8",
                dataType: "json",
                success: function (msg) {
                    console.log(msg);
                },
                error: function (jqXHR, textStatus, errorThrown) {
                    console.log(jqXHR);
                    console.log(textStatus);
                    console.log(errorThrown);
                }
            });

        }, 1000);

    });

</script>

Imports System.Web.Services
Imports System.Web.Script.Services

Partial Class debug
Inherits Page 
    Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        If Not IsPostBack Then

        End If
    End Sub

    <WebMethod(EnableSession:=True)> _
    <ScriptMethod(UseHttpGet:=True)> _
    Public Function Test(ByVal param As String) As String
        Return "testing " & HttpContext.Current.Session("UserID")
    End Function

    <WebMethod(EnableSession:=True)> _
    <ScriptMethod()> _
    Public Function Test2(ByVal param As String) As String
        Return "testing " & HttpContext.Current.Session("UserID")
    End Function
End Class 

Answer 1

The methods need to be Shared:

<WebMethod(EnableSession:=True)> _
<ScriptMethod(UseHttpGet:=True)> _
Public Shared Function Test(ByVal param As String) As String
    Return "testing " & HttpContext.Current.Session("UserID")
End Function

<WebMethod(EnableSession:=True)> _
<ScriptMethod()> _
Public Shared Function Test2(ByVal param As String) As String
   Return "testing " & HttpContext.Current.Session("UserID")
End Function

and also check your script manager allows page methods:

<asp:ScriptManager ID="ScriptManager1" 
EnablePageMethods="true" 
runat="server" />