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RadUpload has been replaced by RadAsyncUpload, Telerik’s next-generation ASP.NET upload component.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 OnClientAdding client-side event occurs when a new row is about to be added to the RadUpload control.

This event occurs for the initial rows that are added when the RadUpload control is first loaded, as well as any rows added in response to the Add button or client-side methods such as addFileInput() .

The event handler receives two parameters:

  1. The instance of the RadUpload control firing the event.

  2. An eventArgs parameter containing the following methods:

    • set_cancel lets you prevent the RadUpload control from adding a new row.

    • get_cancel returns a boolean value indicating whether the addition of a row was cancelled.

    • get_row returns the row that is about to be added (<LI> element)

    • get_rowIndex returns the index of the row

The following example uses the OnClientAdding event to confirm the addition of new rows beyond the initial file inputs:

<telerik:RadUpload  runat="server"  id="RadUpload1"  OnClientAdding="confirmAddition" />
<script type="text/javascript">
    function confirmAddition(upload, args) {
        if (upload.getFileInputs().length >= upload.get_initialFileInputsCount())
            args.set_cancel(!confirm("Are you sure you want to add a new file input?"));


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