$ find RadWindowManager对象始终返回null值

Question

I have a strange problem and I can not understand the reason why it is happening.

In the same *.ascx file, I declare a Telerik:RadWindowManager control and then I call $find() to find that RadWindowManager. However, the method always returns a null value.

Here is the code (included in the same *.ascx):

<%@ Register Assembly="Telerik.Web.UI" Namespace="Telerik.Web.UI" TagPrefix="telerik" %>
<script type="text/javascript">
function init(){
    GetRWndManager();
}

function GetRWndManager() {
    return $find("<%=rwndManager.ClientID%>"); //return null at this step
}

</script>
<telerik:RadWindowManager ID="rwndManager" runat="server" ShowContentDuringLoad="False" VisibleOnPageLoad="False" EnableShadow="true">
</telerik:RadWindowManager>

Answer 1

Ensure you call the init() function (actually, the GetRWndManager() function) after the Sys.Application.Load event, because IScriptControl client-side objects may not be created before that: http://msdn.microsoft.com/en-us/library/bb383829.aspx .

Here is an example:

function init() {
    GetRWndManager();
    Sys.Application.remove_load(init);
}
Sys.Application.add_load(init);

function GetRWndManager() {
    return $find("<%=rwndManager.ClientID%>");
}

Or, use setInterval() and check whether you got an object, until you get an object or reach a maximum of, let's say, 200 attempts.

Also, consider making the function names unique in the UCs to prevent them from overriding each other when there are several instances on the page. The following KB will give you a neat idea: http://www.telerik.com/support/kb/aspnet-ajax/details/using-dynamic-unique-names-for-javascript-functions .