Passing Instance to Shared Method in VB.NET - ajax

Question

I have been thrown in at the deep end with an existing VB.NET project at work. I have never used VB.NET before so I am struggling a little. Does anyone know how to solve the following.
I need to pass an instance to client side and then pass it to a shared method in order to access instance methods from when the shared method.
The starting point is a fileupload control within the HTML of my Contacts.aspx file:
<asp:FileUpload ID="DocUpload1" runat="server" onchange="CallMe();" />
The onchange event calls a javascript method, see below, this uses AJAX PageMethods to called a Shared method in my code behind
This is the script code which is in my Contact.aspx file
<script language="javascript">
function CallMe() {
// call server side method
PageMethods.GetContact(0, CallSuccess, CallFailed, null);
}
// set the destination textbox value with the ContactName
function CallSuccess(res, destCtrl) {
}
// alert message on some failure
function CallFailed(res, destCtrl) {
alert(res.get_message());
}
</script>
This is an example class of the type of thing I want to do, I think I need to use the "instance As Contacts" as an input parameter to the WebMethod function but I don't know how to pass the instance into it:
This is the class within my Contacts.aspx.vb file.
Partial Class Contacts
<System.Web.Services.WebMethod()> _
Public Shared Function GetContact(ByVal instance As Contacts) As String
Return instance.GetContactName() 'This is an instance class which I need to call.
End Function
'This is my instance class which I want to call from the Shared Class.
Public Shared Function GetContactName() As String
Return "Fred Bloggs"
End Function
End Class
If anyone knows the solution please could they update the code as I probably won't be able to understand if you just give a description. I just hope I am along the right tracks.

Answer 1

If I understand you correctly, you want to access a class (your instance) created in the ASP.Net page life-cycle from your PageMethod - eg created during initial page load or file upload etc.
This is not directly possible as PageMethods do not go through the full page life-cycle (they are essentially webservices). So you need to pass some sort of identifier to the client that, when passed back to the server in the PageMethod, can be used to re-create or retrieve your instance.
eg During the initial page load:
session("ContactID") = instance
Your PageMethod might look something like:
Public Shared Function GetContact(ByVal key As String) As String
Return HttpContext.Current.Session(key).GetContactName()
End Function
where the parameter key is the same key you used to store your instance in the session state.
In your javascript:
function CallMe() {
// call server side method
PageMethods.GetContact('ContactID', CallSuccess, CallFailed, null);
}