download.cs

这是一个下载文件使用的类

using System;
using System.Collections.Generic;
using System.Text;
using System.IO;
using System.Threading;
using System.Web;

namespace Cisoft
{
    public static class DownLoad
    {

        //public DownLoad()
        //{
        //}

        // 输出硬盘文件，提供下载 支持大文件、续传、速度限制、资源占用小
		// 输入参数 _Request: Page.Request对象，  _Response: Page.Response对象， _fileName: 下载文件名， _fullPath: 带文件名下载路径， _speed 每秒允许下载的字节数
		// 返回是否成功
		public static bool ResponseFile(HttpRequest _Request,HttpResponse _Response,string _fileName,string _fullPath, long _speed)
		{
			try
			{
				FileStream myFile = new FileStream(_fullPath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
				BinaryReader br = new BinaryReader(myFile);
				try
				{
					_Response.AddHeader("Accept-Ranges", "bytes");
					_Response.Buffer = false;
                    long fileLength = myFile.Length;
                    long startBytes = 0;
                    
					int pack = 10240; //10K bytes
					//int sleep = 200;   //每秒5次   即5*10K bytes每秒
					int sleep = (int)Math.Floor(1000 * (double)pack / (double)_speed) + 1;
					if (_Request.Headers["Range"] != null)
					{
						_Response.StatusCode = 206;
						string[] range = _Request.Headers["Range"].Split(new char[] {'=', '-'});
						startBytes = Convert.ToInt64(range[1]);
					}
					_Response.AddHeader("Content-Length", (fileLength - startBytes).ToString());
					if (startBytes != 0)
					{
						_Response.AddHeader("Content-Range", string.Format(" bytes {0}-{1}/{2}", startBytes, fileLength-1, fileLength));
					}
					_Response.AddHeader("Connection", "Keep-Alive");
					_Response.ContentType = "application/octet-stream";
					_Response.AddHeader("Content-Disposition","attachment;filename=" + HttpUtility.UrlEncode(_fileName,System.Text.Encoding.UTF8) );
 
					br.BaseStream.Seek(startBytes, SeekOrigin.Begin);
					int maxCount = (int) Math.Floor(((double)fileLength - (double)startBytes) / pack) + 1;

					for (int i = 0; i < maxCount; i++)
					{
						if (_Response.IsClientConnected)
						{
							_Response.BinaryWrite(br.ReadBytes(pack));
							Thread.Sleep(sleep);
						}
						else
						{
							i=maxCount;
						}
					}
				}
				catch
				{
					return false;
				}
				finally
				{
					br.Close();
					myFile.Close();
				}
			}
			catch
			{
				return false;
			}
			return true;
		}
	}
}