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The OnClientFilesSelected client-side event occurs when files(s) are selected. This event can be cancelled, which will erase the selectedfiles collection.

The event handler receives two parameters:

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

  2. An eventArgs parameter containing the following methods:

  • get_count returns the count of the selected files.

  • set_cancel lets you cancel the event and prevent items from being uploaded

<telerik:RadAsyncUpload RenderMode="Lightweight" runat="server" ID="RadAsyncUpload1" OnClientFilesSelected="OnClientFilesSelected" MultipleFileSelection="Automatic"></telerik:RadAsyncUpload>
function OnClientFilesSelected(sender, args) {
    var selectedFilesCount = args.get_count();
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