Server-Side Validation

Handle server-side validation using the FileValidating event on postback. This demo accepts normal files and rejects empty uploads, path traversal names, and .tmp files when you submit the page.

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Accepted

Rejected

<!-- .aspx markup -->
<au:AjaxFileUpload ID="Uploader1" runat="server"
 AutoUpload="true"
 ButtonText="Upload File"
 ShowProgress="true"
 OnFileValidating="Uploader1_FileValidating" />

<!-- Code-behind (.aspx.cs) -->
protected void Uploader1_FileValidating(object sender, FileValidatingEventArgs e)
{
 if (e.FileSize == 0)
 {
 e.Cancel = true;
 e.CancelReason = "Empty file.";
 return;
 }
 if (e.FileName.Contains(".."))
 {
 e.Cancel = true;
 e.CancelReason = "Invalid filename.";
 return;
 }
}