.net中 登录 才能下载文件的方法 Response.WriteFile实现下载

protected void Button2_Click(object sender, EventArgs e)
        {  
　　　　　　　　//可以在这里加是否登录的判断
            string fileName = "chracater14.jpg";//客户端保存的文件名 （其他文件格式都支持）
            string filePath = Server.MapPath("../../images/chracater14.jpg");//路径  

            FileInfo fileInfo = new FileInfo(filePath);
            Response.Clear();
            Response.ClearContent();
            Response.ClearHeaders();
            Response.AddHeader("Content-Disposition", "attachment;filename=" + fileName);
            Response.AddHeader("Content-Length", fileInfo.Length.ToString());
            Response.AddHeader("Content-Transfer-Encoding", "binary");
            Response.ContentType = "application/octet-stream";
            Response.ContentEncoding = System.Text.Encoding.GetEncoding("gb2312");
            Response.WriteFile(fileInfo.FullName);
            Response.Flush();
            Response.End();
        }  

string filePath = Server.MapPath(FilePath);//路径
FileInfo fileInfo = new FileInfo(filePath);
if (fileInfo.Exists)
{
Response.Clear();
Response.ClearContent();
Response.ClearHeaders();
Response.AddHeader("Content-Disposition", "attachment;filename=" + Server.UrlEncode(FileName));
Response.AddHeader("Content-Length", fileInfo.Length.ToString());
Response.AddHeader("Content-Transfer-Encoding", "binary");
Response.ContentType = "application/octet-stream";
Response.ContentEncoding = System.Text.Encoding.Default;
Response.WriteFile(fileInfo.FullName);
Response.Flush();
Response.End();
}