Question

Anyone got any ideas?

The above error occurs when the following code is run:

    Sys.WebForms.PageRequestManager.getInstance().add_endRequest(RequestCompleted);

Within this block:

<script language="javascript" type="text/javascript">
    var postBackElement;

    Sys.WebForms.PageRequestManager.getInstance().add_endRequest(RequestCompleted);
    Sys.WebForms.PageRequestManager.getInstance().add_initializeRequest(InitializeRequestHandler);

    function InitializeRequestHandler(sender, args) {
        //set the postBackElement
        postBackElement = args.get_postBackElement();
    }

Answer 1

You need to handle the RequestCompleted event if you’re going to use it:

function RequestCompleted(sender, args) {
   // Do what you need to do here
}

If you don’t need to handle the event, just remove this line from your markup:

Sys.WebForms.PageRequestManager.getInstance().add_endRequest(RequestCompleted);