将gridview导出到excel文件时，Response.End（）会生成错误

I have this code:

我有这个代码:

protected void ibtGenerateReport_Click(object sender, ImageClickEventArgs e)
{
    string filename = "report.xls";             

    StringWriter stringWriter = new StringWriter();
    HtmlTextWriter htmlWrite = new HtmlTextWriter(stringWriter);
    DataGrid DataGrd = new DataGrid();            
    DataGrd.DataSource = odsLSRAudit;
    DataGrd.DataBind();

    DataGrd.RenderControl(htmlWrite);            

    System.IO.StreamWriter vw = new System.IO.StreamWriter(filename, true);
    stringWriter.ToString().Normalize();
    vw.Write(stringWriter.ToString());
    vw.Flush();
    vw.Close();
    WriteAttachment(filename, "application/vnd.ms-excel", stringWriter.ToString());           
}

public static void WriteAttachment(string FileName, string FileType, string content)
{
    HttpResponse Response = System.Web.HttpContext.Current.Response;
    Response.ClearHeaders();
    Response.AppendHeader("Content-Disposition", "attachment; filename=" + FileName);
    Response.ContentType = FileType;
    Response.Write(content);            
    Response.End();
}
protected void ib