<add key="键值" value="\\IP地址\Attachments" />

<identITy imPErsonate="true" userName="docshareuser" password="密码" />

context.Response.AppendHeader("Content-Length", fileSize.ToString());
context.Response.CacheControl = HttpCacheability.Public.ToString();
context.Response.Cache.AppendCacheExtension("max-age=" + 365 * 24 * 60 * 60);
context.Response.Cache.SetExpires(DateTime.Now.AddYears(1));
context.Response.AppendHeader("ETag", "Never_Modify");
context.Response.Cache.SetETag("Never_Modify");
context.Response.Cache.SetLastModified(DateTime.Now.AddMinutes(-1));
 
context.Response.TransmitFile(filePath);

FileStream fs = new FileStream(filePath, FileMode.Open);
    byte[] bytes = new byte[(int)fs.Length];
    fs.Read(bytes, 0, bytes.Length);
    fs.Close();
    Response.ContentType = "application/octet-stream";
    //通知浏览器下载文件而不是打开 
    Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(fileName, System.Text.Encoding.UTF8));
    context.Response.BinaryWrite(bytes);
    context.Response.Flush();
    context.Response.End();