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.

Drag & drop files here, or paste from clipboard

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;
    }
}