ScriptManager.RegisterClientScriptBlock duplicates JavaScript on Async PostBack (ASP.NET AJAX)

I am creating a UserControl of the Yahoo Calendar for use in Microsoft ASP.NET AJAX and am close to completion at this point. However two bugs remain. The one I need some assistance on is regarding the ScriptManager.RegisterClientScriptBlock.

When the user control is used on a site and is not initialized immediately on the page, but is started instead on the page after the postback (or if the control is turned on/off, it may be a later postback and not the immediate one), so you would use the ScriptManager.RegisterClientScriptBlock to add the JavaScript to the script manager. And at this time, this works quite well. However, what doesn't work, is that I have no way of preventing this from stopping once it is turned on and the script multiplies, so many instances of the object are the displayed on the page.

This can be seen at http://www.gmitravelinc.com/yahoo/

All visible controls immediately seen are intialized and are working properly. Click "Test" and "Date 5" will be added to the page asynchronosly within the group. Click the button, now labeled "Testing!" and both "Date 6" and "Date 5", part of a similar control type, will begin to reproduce on the page.

How do I change my code to prevent this?

String stringScript = String.Empty;
stringScript = @"
<script type=""text/javascript"" id=""" + this.ClientID + @"Script"">
var prm = Sys.WebForms.PageRequestManager.getInstance();
prm.add_initializeRequest(initializeRequest);
prm.add_pageLoaded(pageLoaded);
var _postBackElement;
 
function initializeRequest(sender, e)
{
   if (prm.get_isInAsyncPostBack())
   {
      e.set_cancel(true);
   }
   _postBackElement = e.get_postBackElement();
}
 
function pageLoaded(sender, e)
{
   YAHOO.util.Event.onDOMReady(function ()
   {
";
					if (boolReadOnly)
					{
						stringScript += @"
      document.getElementById(""" + stringTargetControlID + @""").readOnly = true;
";
					}
					stringScript += @"
      function onButtonClick()
      {
         oCalendarMenu.setBody(""&#32;"");
         oCalendarMenu.body.id = """ + this.ClientID + @"calendarcontainer"";
         oCalendarMenu.render(this.get(""container""));
         oCalendarMenu.align();
         var oCalendar = new YAHOO.widget.Calendar(""" + this.ClientID + @"buttoncalendar"", oCalendarMenu.body.id);
";
					if (boolNavigation)
					{
						stringScript += @"
         oCalendar.cfg.setProperty(""navigator"", true);
";
					}
					if (!String.IsNullOrEmpty(stringMinDate))
					{
						stringScript += @"
         oCalendar.cfg.setProperty(""mindate"", """ + stringMinDate + @""");
";
					}
					if (!String.IsNullOrEmpty(stringMaxDate))
					{
						stringScript += @"
         oCalendar.cfg.setProperty(""maxdate"", """ + stringMaxDate + @""");
";
					}
					if (!String.IsNullOrEmpty(stringPageDate))
					{
						stringScript += @"
         oCalendar.cfg.setProperty(""pagedate"", """ + stringPageDate + @""");
";
					}
					if (!String.IsNullOrEmpty(stringHightlight))
					{
						stringScript += @"
         oCalendar.addRenderer(""" + stringHightlight + @""", oCalendar.renderCellStyleHighlight1);
";
					}
					if (!String.IsNullOrEmpty(stringSoldOut))
					{
						stringScript += @"
         oCalendar.addRenderer(""" + stringSoldOut + @""", oCalendar.renderBodyCellRestricted);
";
					}
					stringScript += @"
         var stDate = document.getElementById(""" + stringTargetControlID + @""");
         if (stDate.value != """")
         {
            oCalendar.select(stDate.value);
            var selectedDates = oCalendar.getSelectedDates();
            if (selectedDates.length > 0)
            {
               var firstDate = selectedDates[0];
               oCalendar.cfg.setProperty(""pagedate"", (firstDate.getMonth()+1) + ""/"" + firstDate.getFullYear());
            }
         }
         oCalendar.render();
         oCalendar.changePageEvent.subscribe(function ()
         {
            window.setTimeout(function ()
            {
               oCalendarMenu.show();
            }, 0);
         });
         oCalendar.selectEvent.subscribe(function (p_sType, p_aArgs)
         {
            var aDate;
            if (p_aArgs)
            {
               aDate = p_aArgs[0][0];
               YAHOO.util.Dom.get(""" + stringTargetControlID + @""").value = aDate[1] + ""/"" + aDate[2] + ""/"" + aDate[0];
            }
            oCalendarMenu.hide();
         });
         this.unsubscribe(""click"", onButtonClick);
      }
      var oCalendarMenu = new YAHOO.widget.Overlay(""" + this.ClientID + @"calendarmenu"");
      var oButton = new YAHOO.widget.Button({type: ""menu"", 
                                             id: """ + this.ClientID + @"calendarpicker"", 
                                             label: ""Choose A Date"", 
                                             menu: oCalendarMenu, 
                                             container: """ + this.ClientID + @"datefields"" });
      oButton.on(""click"", onButtonClick);
   });
}
</script>
";
					writer.Write(@"
        <span id=""" + this.ClientID + @"datefields"">
" + stringScript + @"
        </span>
");
 
if (IsPostBack)
{
	ScriptManager.RegisterClientScriptBlock(Page, typeof(YahooCalendar), this.ClientID + "ScriptA", stringScript, false);
}

Select allOpen in new window