字符串输出形成下载文件

public void down(string fileName, string content)
    {

        System.Web.HttpContext.Current.Response.Clear();

        System.Web.HttpContext.Current.Response.AddHeader("Content-Disposition", "attachment; filename=" + fileName);

        System.Web.HttpContext.Current.Response.AddHeader("Content-Length", content.Length.ToString());

        System.Web.HttpContext.Current.Response.ContentType = "application/octet-stream";
        System.Web.HttpContext.Current.Response.ContentEncoding = System.Text.Encoding.Default;

        System.Web.HttpContext.Current.Response.Filter.Close();
        System.Web.HttpContext.Current.Response.AppendHeader("Content-Disposition", "attachment;filename=" + fileName);

        System.Web.HttpContext.Current.Response.Write(content);

        System.Web.HttpContext.Current.Response.End();
    }