ASP.NET中实现文件下载功能

    //TransmitFile实现下载
    protected void Button1_Click(object sender, EventArgs e)
     {
        /*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=admin.exe");
       string filename = Server.MapPath("~/signserver/fileupload/admin.exe");
       Response.TransmitFile(filename);
     }

    //WriteFile实现下载
    protected void Button2_Click(object sender, EventArgs e)
     {
        /*using System.IO;*/

        string fileName ="admin.exe";//客户端保存的文件名
        string filePath=Server.MapPath("~/signserver/fileupload/admin.exe");//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();
     }

    //WriteFile分块下载
    protected void Button3_Click(object sender, EventArgs e)
     {
        /*using System.IO;*/

        string fileName = "admin.exe";//客户端保存的文件名
        string filePath = Server.MapPath("~/signserver/fileupload/admin.exe");//路径

        FileInfo fileInfo = new FileInfo(filePath);

        if (fileInfo.Exists == true)
         {
            const long ChunkSize = 102400;//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();
            FileStream iStream = 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();
         }
     }

    //流方式下载
    protected void Button4_Click(object sender, EventArgs e)
     {

        /*using System.IO;*/

        string fileName = "admin.exe";//客户端保存的文件名
        string filePath = Server.MapPath("~/signserver/fileupload/admin.exe");//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();

     }