New to Telerik UI for ASP.NET AJAX? Download free 30-day trial


RadUpload has been replaced by RadAsyncUpload, Telerik’s next-generation ASP.NET upload component. If you are considering Telerik’s Upload control for new development, check out the documentation of RadAsyncUpload or the control’s product page. If you are already using RadUpload in your projects, you may be interested in reading how easy the transition to RadAsyncUpload is and how you can benefit from it in this blog post. The official support for RadUpload has been discontinued in June 2013 (Q2’13), although it is still be available in the suite. We deeply believe that RadAsyncUpload can better serve your upload needs and we kindly ask you to transition to it to make sure you take advantage of its support and the new features we constantly add to it.

The OnClientSubmitting client-side event occurs when a postback that uploads files is about to occur.

The event handler receives two parameters:

  1. The instance of the RadProgressManager that fires the event.

  2. An eventArgs parameter containing the following methods:

    • set_cancel lets you prevent the postback.

    • get_cancel returns whether the postback has been cancelled.

The following example uses the OnClientSubmitting event to prevent the postback if the files to upload are invalid:

<script type="text/javascript">
    function ValidateSubmission(source, eventArgs) {
        var upload = $find("<%= RadUpload1.ClientID %>");
        if (eventArgs.get_cancel())
            alert("Submission blocked: one or more files have the wrong type!");

<telerik:radprogressmanager id="RadProgressManager1" runat="server" onclientsubmitting="ValidateSubmission" />
<telerik:radupload id="RadUpload1" runat="server" allowedfileextensions=".prn,.txt" />
<asp:Button ID="Button1" runat="server" Text="Submit" />

See Also

In this article