文件以附件形式下载的方法

 1// 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
 2        // 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
 3        // 返回是否成功
 4        public static bool ResponseFile(HttpRequest _Request,HttpResponse _Response,string _fileName,string _fullPath, long _speed)
 5        {
 6            try
 7            {
 8                FileStream myFile = new FileStream(_fullPath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
 9                BinaryReader br = new BinaryReader(myFile);
10                try
11                {
12                    _Response.AddHeader("Accept-Ranges", "bytes");
13                    _Response.Buffer = false;
14                    long fileLength = myFile.Length;
15                    long startBytes = 0;
16     
17                    int pack = 102400; //10K bytes
18                    //int sleep = 200;   //每秒5次   即5*10K bytes每秒
19                    int sleep = (int)Math.Floor(1000 * pack / _speed) + 1;
20                    if (_Request.Headers["Range"] != null)
21                    {
22                        _Response.StatusCode = 206;
23                        string[] range = _Request.Headers["Range"].Split(new char[] {'=', '-'});
24                        startBytes = Convert.ToInt64(range[1]);
25                    }
26                    _Response.AddHeader("Content-Length", (fileLength - startBytes).ToString());
27                    if (startBytes != 0)
28                    {
29                        _Response.AddHeader("Content-Range", string.Format(" bytes {0}-{1}/{2}", startBytes, fileLength-1, fileLength));
30                    }
31                    _Response.AddHeader("Connection", "Keep-Alive");
32                    _Response.ContentType = "application/octet-stream";
33                    _Response.AddHeader("Content-Disposition","attachment;filename=" + HttpUtility.UrlEncode(_fileName,System.Text.Encoding.UTF8) );
34 
35                    br.BaseStream.Seek(startBytes, SeekOrigin.Begin);
36                    int maxCount = (int) Math.Floor((fileLength - startBytes) / pack) + 1;
37
38                    for (int i = 0; i < maxCount; i++)
39                    {
40                        if (_Response.IsClientConnected)
41                        {
42                            _Response.BinaryWrite(br.ReadBytes(pack));
43                            Thread.Sleep(sleep);
44                        }
45                        else
46                        {
47                            i=maxCount; 
48                        }
49                    }
50                }
51                catch
52                {
53                    return false;
54                }
55                finally
56                {
57                    br.Close();
58                    myFile.Close();
59                }
60            }
61            catch
62            {
63                return false;
64            }
65            return true;
66        }