ErrorCode When I Start DirectEventArgs e with Export

I'm Chinese,my description mabe not accurate
I want to Export a file in DirectEventArgs e,then i can use EventMask and Confirmation property,but,it's happen a ErrorCode,just open
a window with Strange symbols,http status is 200,

Code:

---

protected void ExportClick(object sender,DirectEventArgs e)
{
  DownLoadFileFromByte(file.FileBytes,"FileName");
}
protected void DownLoadFileFromByte(byte[] bytes, string fileName)
{
        Response.ContentType = "application/octet-stream";
        Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(fileName,
        System.Text.Encoding.UTF8));
        Response.BinaryWrite(bytes);
        Response.Flush();
        Response.End();
}

---

and then it's happen a ErrorCode,and then i just change DirectEvent to OnClick="ExportClick",change (DirectEventArgs e)
to (EventArgs e),and its's ok,nothing error,but i can't use EventMask and Confirmation,anyone know?how to solve this,it's not good
for user although it's work