using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.IO;

public partial class _Default : System.Web.UI.Page
{
    private void Page_Load(object sender, System.EventArgs e)
    {
        Response.Buffer = false;

        string file = "D:/bmp.bmp";

        FileInfo fi = new FileInfo(file);

        long startPos = 0;

        //所传输的文件长度

        long fileTranLen = fi.Length;

        //断点续传请求

        if (Request.Headers["Range"] != null)
        {

            Response.StatusCode = 206;

            startPos = long.Parse(Request.Headers["Range"].Replace("bytes=", "").Split('-')[0]);

            fileTranLen -= startPos;

            //Response.AddHeader("Accept-Ranges", "bytes");

            //Content-Range: bytes [文件块的开始字节]-[传输文件的总大小]/[文件的总大小]

            Response.AddHeader("Content-Range", string.Format("bytes {0}-{1}/{2}", startPos, fileTranLen, fi.Length));

        }

        Response.AddHeader("Content-Length", fileTranLen.ToString());

        //基本的文件下载报文头

        Response.ContentType = "application/octet-stream";

        Response.AddHeader("Content-Disposition", "attachment; filename=" + fi.Name);

        //简单的流拷贝

        System.IO.Stream fileStream = System.IO.File.OpenRead(file);

        fileStream.Position = startPos;

        Response.End();

    }

    class PartDownload
    {
        private int offset;
        private int count;
        private int filesize;
        private string filename;
        HttpRequest Request;
        HttpResponse Response;

        public PartDownload(string filename,int filesize)
        {
            this.filename = filename;
            this.filesize = filesize;
            this.count = filesize;
            this.offset = 0;

            Request=HttpContext.Current.Request;
            Response=HttpContext.Current.Response;
            Response.Buffer = false;

            if (Request.Headers["Range"] != null)
            {
                Response.StatusCode = 206;
                offset = int.Parse(Request.Headers["Range"].Replace("bytes=", "").Split('-')[0]);
                count = filesize - offset;
                //Response.AddHeader("Accept-Ranges", "bytes");
                //Content-Range: bytes [文件块的开始字节]-[传输文件的总大小]/[文件的总大小]
                Response.AddHeader("Content-Range", string.Format("bytes {0}-{1}/{2}", offset, count, filesize));
            }

            Response.AddHeader("Content-Length",filesize.ToString());
            Response.ContentType = "application/octet-stream";
            Response.AddHeader("Content-Disposition", "attachment; filename=" + filename);
        }

        public void BinaryWrite(byte[] buf)
        {
           
        }
    }

}