AJAX Control Toolkit - AjaxFileUpload 上传问题

Question

前台代码:
<asp:AjaxFileUpload ID="AjaxFileUpload1" runat="server" ThrobberID="iThrobber" AllowedFileTypes="pdf" MaximumNumberOfFiles="10" OnUploadComplete="AjaxFileUpload1_UploadComplete"/>后台代码:
protected void AjaxFileUpload1_UploadComplete(object sender, AjaxControlToolkit.AjaxFileUploadEventArgs e)
{
    string filePath = "~/test/" + new FileInfo(e.FileName).Name;
    AjaxFileUpload1.SaveAs(MapPath(filePath));
}
当页面不传递?参数时, 功能正常, 但是如果带?参数时, 则会弹出错误
即:
localhost/upload.aspx                没问题
localhost/upload.aspx?aa=bb    出错
错误: Sys.ArgumentException: Cannot deserialize. The data does not correspond to valid JSON.
Parameter name: data
请帮忙解决, 非常感谢!AjaxFileUploadAJAX Control Toolkit