.net 实现附件下载

Question

我想点击下载（LinkButton），就能下载我选择的这个附件，但是总是找不到文件，附件已经上传到数据库里，请各位大虾帮我看看
protected void LinkButtonDownload_click(object sender, EventArgs e)
    {
        LinkButton lbtn=(LinkButton)sender;
        string id=lbtn.CommandArgument;        string url = "select * from AnswerInfo where anwid="+id;
        DataSet ds = new dbBLL().QueryDataSet(url);
        string fileName = ViewState["upload"].ToString();//客户端保存的文件名
        string path = HttpUtility.UrlEncode(ds.Tables[0].Rows[0]["upload"].ToString());//路径
        string filePath = "~/img/" + path;        FileInfo fileInfo = new FileInfo(filePath);
        Response.Clear();
        Response.ClearContent();
        Response.ClearHeaders();
        Response.AddHeader("Content-Disposition", "attachment;filename=" +filePath);        Response.AddHeader("Content-Length", fileInfo.Length.ToString()); //这里找不到文件         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();    }

Answer 1

//下载的四种方法    protected void Button1_Click(object sender, EventArgs e)
        {
            //TransmitFile实现下载            /**/
            /*
             微软为Response对象提供了一个新的方法TransmitFile来解决使用Response.BinaryWrite
             下载超过400mb的文件时导致Aspnet_wp.exe进程回收而无法成功下载的问题。
             代码如下：
            */            Response.ContentType = "application/x-zip-compressed";
            Response.AddHeader("Content-Disposition", "attachment;filename=keji.rar");
            string filename = Server.MapPath("keji.rar");
            Response.TransmitFile(filename);
            Response.Write("<script language=\"javascript\" type=\"text/javascript\">");
            Response.Write("alert(\"下载成功\");");
            Response.Write("window.location.href=\"C_SC.aspx\";");
            Response.Write("</script>");
        }        protected void Button2_Click(object sender, EventArgs e)
        {            //WriteFile实现下载
            string fileName = "ceshi.rar";//客户端保存的文件名
            string filePath = Server.MapPath("keji.rar");//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();
        }        protected void Button3_Click(object sender, EventArgs e)
        {
            //WriteFile分块下载            string fileName = "GhostXP.iso";//客户端保存的文件名
            string filePath = Server.MapPath("GhostXP7.7.iso");//路径            System.IO.FileInfo fileInfo = new System.IO.FileInfo(filePath);            if (fileInfo.Exists == true)
            {
                const long ChunkSize = 409600;//100K 每次读取文件，只读取100Ｋ，这样可以缓解服务器的压力
                byte[] buffer = new byte[ChunkSize];                Response.Clear();
                System.IO.FileStream iStream = System.IO.File.OpenRead(filePath);
                long dataLengthToRead = iStream.Length;//获取下载的文件总大小
                Response.ContentType = "application/octet-stream";
                Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(fileName));
                while (dataLengthToRead > 0 && Response.IsClientConnected)
                {
                    int lengthRead = iStream.Read(buffer, 0, Convert.ToInt32(ChunkSize));//读取的大小
                    Response.OutputStream.Write(buffer, 0, lengthRead);
                    Response.Flush();
                    dataLengthToRead = dataLengthToRead - lengthRead;
                }
                Response.Close();
            }
        }        //字符流方式下载文件
        protected void Button4_Click(object sender, EventArgs e)
        {
            string fileName = "ce2.rar";//客户端保存的文件名
            string filePath = Server.MapPath("keji.rar");//路径            //以字符流的形式下载文件
            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));
            Response.BinaryWrite(bytes);
            Response.Flush();
            Response.End();
        }