Asp.net 实现断点续传 下载大文件

**//// <summary>
x _0O%f+K)B5D        /// 支持断点续传的下载大文件的函数 中博IT教育网4P z/2b,h-q `
        /// </summary>
_;B$A.} S8E#@ D I        /// <param name="downloadFilePath">被下载文件的路径，相对和绝对都可以</param>
K I g(h { D V        /// <param name="showFileName">显示给用户的文件名，可以为空</param>
.p9a1X j;[        /// <param name="fileType">要下载的文件类型，如果不确定，请留空</param>
E `6G5F L n(y y /        /// <remarks>用于大文件的下载</remarks>
;h1i'^+Q t T P5w F j5a        public static void BigFileDownload(string downloadFilePath, string showFileName, string fileType) 中博IT教育网3r @$f"W y
        { 中博IT教育网)m t J L b I3S [4s W p
            downloadFilePath = downloadFilePath.Trim();
6u D0/)h E l ^ _ p P e i            if(string.Empty == downloadFilePath) 中博IT教育网%on4^"] t n%E b
                ShowErrorMessage("没有指定要下载的文件路径！");
1l4t [$g ]3d/y8c            
1b2M t9h{ x o8[8N b            if(downloadFilePath.IndexOf(":") < 0)
D(o I*W m                downloadFilePath = System.Web.HttpContext.Current.Server.MapPath(downloadFilePath);
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(t e {'X5C.Z S m E            showFileName = showFileName.Trim();
#I f _ s)H/D            if(string.Empty == showFileName) 中博IT教育网 J S m;@;P)~
                showFileName = Path.GetFileName(downloadFilePath);
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n:| w h(z Q ]*D s            showFileName = System.Web.HttpUtility.UrlEncode(System.Web.HttpContext.Current.Request.ContentEncoding.GetBytes(showFileName)); 中博IT教育网 A A c F-x*j
             中博IT教育网 z j g q g K1/;Y H A
            fileType = fileType.Trim(); 中博IT教育网 y T2I${ g%Q D
            if(string.Empty == fileType)
'~ Y m k Y W f                fileType = "application/octet-stream";
R c d u8l#U h M o J 中博IT教育网-l B:^ X { p
            System.Web.HttpContext.Current.Response.Clear(); 中博IT教育网 M V)~ @ X z"] l ` g X
            Stream objStream = null; 中博IT教育网$z y(p;V"z e$c"^
            byte[] btBuffer = new byte[8192]; // 1024*8 = 8Kb 中博IT教育网1f"[;/ { p.K,J u T T
            int intLength = 0;
U#@ X o ` x&I,a)D%V            long lngData2Read = 0;
j8q R ~+k;[ i s            try 中博IT教育网 o o ` r,P
            {
|:v T-q0P J7W!@                using(objStream = new FileStream(downloadFilePath, FileMode.Open, FileAccess.Read, FileShare.Read)) 中博IT教育网G1x g O c } ^ k c
                {
q"q eE/^4E e!@                    lngData2Read = objStream.Length;
G {+i!r g A,] J                     中博IT教育网*x$B&^2P#t T
                    输出HTTP头信息#region 输出HTTP头信息 中博IT教育网)} ~%`:{ x6`
                    
A o } f$A ~3^                    long lngP = 0;
#Y Q;b/x/R s H6Y                    if(null != System.Web.HttpContext.Current.Request.Headers["Range"])
w&Y F)? J                    { 中博IT教育网%q S k Q U
                        System.Web.HttpContext.Current.Response.StatusCode = 206;
#S q+n:M I k8/                        lngP = long.Parse(System.Web.HttpContext.Current.Request.Headers["Range"].Replace("bytes=","").Replace("-","")); 中博IT教育网 } W Q9T-Q
                    }
c.x C I f                    if(0 != lngP)
C(F#j+W7_ y                    {
h Z!z _ k m3z"h1Z L s                        System.Web.HttpContext.Current.Response.AddHeader("Content-Range","bytes " + lngP.ToString() + "-" + ((long)(lngData2Read - 1)).ToString() + "/" + lngData2Read.ToString());                     中博IT教育网 x D/A5F1T
                    }
hw!^ i:W%] Y0G L                    System.Web.HttpContext.Current.Response.AddHeader("Content-Length",((long)(lngData2Read - lngP)).ToString());
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+]!R L3w-J&]+y)`"E                    System.Web.HttpContext.Current.Response.ContentType = fileType;
k q,k)v Y%}(J                    System.Web.HttpContext.Current.Response.AddHeader("Content-Disposition", "attachment;filename=" + showFileName);
$^&I#Y'l K,|                    
p ? ? l1_.g-O                    #endregion 中博IT教育网 ? S1X:v:R
                     中博IT教育网 |7x t3n)X#O
                    while(lngData2Read > 0) <
4000
span style="display:none;">中博IT教育网 z C f^"p!d!~ y
                    { 中博IT教育网 ~ e r y h"w;H
                        if(HttpContext.Current.Response.IsClientConnected)
(M5K%V c-c / y+C                        { 中博IT教育网(b M*? k m-G
                            intLength = objStream.Read(btBuffer, 0, 8192);
/|&o'v%g7/#B o:T @                            HttpContext.Current.Response.OutputStream.Write(btBuffer, 0, intLength); 中博IT教育网(U8l v T+|1d
                            HttpContext.Current.Response.Flush(); 中博IT教育网 _0Q:M w Z | y
                            lngData2Read -= intLength;
E*qa1D { S$s n J7? `                            btBuffer = new byte[8192]; 中博IT教育网,J%s9v'B g5H5V7`(^2l
                        } 中博IT教育网)L.@ | d+| G
                        else
)v G d"i N0A                        { 中博IT教育网 H l u"l K Ed8h n
                            lngData2Read = -1; 中博IT教育网 f { r bu R }7/$] x
                        }
A m [ e2P                    }
[;L#H ] j9j%U                } 中博IT教育网0|"@ _ / ?*C n%P;/
            } 中博IT教育网$J9h4K q K V$?
            catch(Exception ex)
@-Y3b$V1y Q            { 中博IT教育网 E6P [#k J { Q g(V
                ShowErrorMessage(ex.Message); 中博IT教育网6o8M J.X x X t
            } 中博IT教育网/@ k*z W:l
            // 结束文件下载，此句不可缺少，否则会把本页的HTML代码一起下载文件里 中博IT教育网-G } j/I4/%b m4~ _
            HttpContext.Current.Response.End();
-s l S5t R u / L C/t8D        }
r,u A'y ` j Z;_ [ P I 中博IT教育网'^ X D|3O
        /**//// <summary>
.L4~f6o K J%t @        /// 输出错误信息给用户，采用客户端弹出框的方式 中博IT教育网 Y9G2F h I R J N W j
        /// </summary>
b G,X'E H'f E K)J        /// <param name="errorMessage">错误信息的内容</param>
;d7y u/r,u!M r T R        internal static void ShowErrorMessage(string errorMessage) 中博IT教育网)G1l.L l b
        {
(p/X ^ f E m            errorMessage = errorMessage.Replace("", "/""); 中博IT教育网+U(r /4M N r S A&^%e m / c
            System.Web.HttpContext.Current.Response.Write("<script language=javascript>");
` C9z8I,s6Z L F            System.Web.HttpContext.Current.Response.Write("alert("); 中博IT教育网,` U9w"B t(C
            System.Web.HttpContext.Current.Response.Write(errorMessage);
+` K-S(X z$K6g;c Z            System.Web.HttpContext.Current.Response.Write(");</script>"); 中博IT教育网 A T1h-/!h;o"S$V |
            System.Web.HttpContext.Current.Response.End(); 中博IT教育网 n;T w F%C:[ @r
        }