关于C#实现下载的问题：如果文件名含有空格,文件名的空格会变成"+"号，下载后的文件名跟原来的不一样，请问怎么解决?

附下载源码:
private void LinkButton_Click(object sender,System.EventArgs e) 
{ 
          string  path = Server.MapPath("aa/uploadbooks.xml");       
          System.IO.FileInfo file = new System.IO.FileInfo(path);       
          Response.Clear();       
          Response.Charset="GB2312";       
          Response.ContentEncoding=System.Text.Encoding.UTF8;       
          Response.AddHeader("Content-Disposition","attachment;filename=" + Server.UrlEncode(file.Name));  
          Response.AddHeader("Content-Length",file.Length.ToString());       
          Response.ContentType = "application/ms-excel";       
          Response.WriteFile(file.FullName);       
          Response.End(); 
}