Excel文件的格式由文件扩展名指定（Excel从gridview导出）

The file you are trying to open < > is in a different format than specified by the file extension.  Verify that the file is not corrupted and is from a trusted source before opening the file.  Do you want to open the file now?

        HttpContext.Current.Response.Clear();
        HttpContext.Current.Response.AddHeader(\"content-disposition\", string.Format(\"attachment; filename={0}\", \"Single_Raw.xls\"));
        HttpContext.Current.Response.ContentType = \"application/vnd.ms-excel\";

    using (StringWriter sw = new StringWriter())
    {
        using (HtmlTextWriter htw = new HtmlTextWriter(sw))
        {
           // some code

            HttpContext.Current.Response.Write(sw.ToString());
            HttpContext.Current.Response.End();
        }
    }