怎样恢复能在asp.net中使用c#下载文件 – >最好的方法(对于大文件也是如此)

看下面的处理程序：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

namespace FileExplorer
{
    /// <summary>
    /// Summary description for HandlerForMyFE
    /// </summary>
    public class HandlerForMyFE : IHttpHandler,System.Web.SessionState.IRequiresSessionState
    {

        private HttpContext _context;
        private HttpContext Context
        {
            get
            {
                return _context;
            }
            set
            {
                _context = value;
            }
        }

        public void ProcessRequest(HttpContext context)
        {
            Context = context;
            string filePath = context.Request.QueryString["Downloadpath"];
            filePath = context.Server.MapPath(filePath);

            if (filePath == null)
            {
                return;
            }

            System.IO.StreamReader streamReader = new System.IO.StreamReader(filePath);
            System.IO.BinaryReader br = new System.IO.BinaryReader(streamReader.BaseStream);

            byte[] bytes = new byte[streamReader.BaseStream.Length];

            br.Read(bytes,(int)streamReader.BaseStream.Length);

            if (bytes == null)
            {
                return;
            }

            streamReader.Close();
            br.Close();
            string fileName = System.IO.Path.GetFileName(filePath);
            string MimeType = GetMimeType(fileName);
            string extension = System.IO.Path.GetExtension(filePath);
            char[] extension_ar = extension.ToCharArray();
            string extension_Without_dot = string.Empty;
            for (int i = 1; i < extension_ar.Length; i++)
            {
                extension_Without_dot += extension_ar[i];
            }

            //if (extension == ".jpg")
            //{ // Handle *.jpg and
            //    WriteFile(bytes,fileName,"image/jpeg jpeg jpg jpe",context.Response);
            //}
            //else if (extension == ".gif")
            //{// Handle *.gif
            //    WriteFile(bytes,"image/gif gif",context.Response);
            //}

            if (HttpContext.Current.Session["User_ID"] != null)
            {
                WriteFile(bytes,MimeType + " " + extension_Without_dot,context.Response);
            }
        }

        private void WriteFile(byte[] content,string fileName,string contentType,HttpResponse response)
        {
            response.Buffer = true;
            response.Clear();
            response.ContentType = contentType;

            response.AddHeader("content-disposition","attachment; filename=" + fileName);

            response.BinaryWrite(content);
            response.Flush();
            response.End();
        }

        private string GetMimeType(string fileName)
        {
            string mimeType = "application/unknown";
            string ext = System.IO.Path.GetExtension(fileName).ToLower();
            Microsoft.Win32.RegistryKey regKey = Microsoft.Win32.Registry.ClassesRoot.OpenSubKey(ext);
            if (regKey != null && regKey.GetValue("Content Type") != null)
                mimeType = regKey.GetValue("Content Type").ToString();
            return mimeType;
        }

        public bool IsReusable
        {
            get
            {
                return false;
            }
        }
    }
}

我使用这个处理程序下载我的文件而不直接在浏览器中打开它们 – > (使用查询字符串路径)

如何让我的文件恢复？

我在互联网下载管理器中没有这个选项！

解决方法

根据要求,这是答案的“清理”版本：

public static bool DownloadFileMethod(HttpContext httpContext,string filePath,long speed)
{
    // Many changes: mostly declare variables near use
    // Extracted duplicate references to HttpContext.Response and .Request
    // also duplicate reference to .HttpMethod

    // Removed try/catch blocks which hid any problems
    var response = httpContext.Response;
    var request = httpContext.Request;
    var method = request.HttpMethod.ToUpper();
    if (method != "GET" &&
        method != "HEAD")
    {
        response.StatusCode = 501;
        return false;
    }

    if (!File.Exists(filePath))
    {
        response.StatusCode = 404;
        return false;
    }

    // Stream implements IDisposable so should be in a using block
    using (var myFile = new FileStream(filePath,FileMode.Open,FileAccess.Read,FileShare.ReadWrite))
    {
        var fileLength = myFile.Length;
        if (fileLength > Int32.MaxValue)
        {
            response.StatusCode = 413;
            return false;
        }

        var lastUpdateTiemStr = File.GetLastWriteTimeUtc(filePath).ToString("r");
        var fileName = Path.GetFileName(filePath);
        var fileNameUrlEncoded = HttpUtility.UrlEncode(fileName,Encoding.UTF8);
        var eTag = fileNameUrlEncoded + lastUpdateTiemStr;

        var ifRange = request.Headers["If-Range"];
        if (ifRange != null && ifRange.Replace("\"","") != eTag)
        {
            response.StatusCode = 412;
            return false;
        }

        long startBytes = 0;

        // Just guessing,but I bet you want startBytes calculated before
        // using to calculate content-length
        var rangeHeader = request.Headers["Range"];
        if (rangeHeader != null)
        {
            response.StatusCode = 206;
            var range = rangeHeader.Split(new[] {'=','-'});
            startBytes = Convert.ToInt64(range[1]);
            if (startBytes < 0 || startBytes >= fileLength)
            {
                // TODO: Find correct status code
                response.StatusCode = (int) HttpStatusCode.BadRequest;
                response.StatusDescription =
                    string.Format("Invalid start of range: {0}",startBytes);
                return false;
            }
        }

        response.Clear();
        response.Buffer = false;
        response.AddHeader("Content-MD5",GetMD5Hash(filePath));
        response.AddHeader("Accept-Ranges","bytes");
        response.AppendHeader("ETag",string.Format("\"{0}\"",eTag));
        response.AppendHeader("Last-Modified",lastUpdateTiemStr);
        response.ContentType = "application/octet-stream";
        response.AddHeader("Content-Disposition","attachment;filename=" +
                                                    fileNameUrlEncoded.Replace("+","%20"));
        var remaining = fileLength - startBytes;
        response.AddHeader("Content-Length",remaining.ToString());
        response.AddHeader("Connection","Keep-Alive");
        response.ContentEncoding = Encoding.UTF8;

        if (startBytes > 0)
        {
            response.AddHeader("Content-Range",string.Format(" bytes {0}-{1}/{2}",startBytes,fileLength - 1,fileLength));
        }

        // BinaryReader implements IDisposable so should be in a using block
        using (var br = new BinaryReader(myFile))
        {
            br.BaseStream.Seek(startBytes,SeekOrigin.Begin);

            const int packSize = 1024*10; //read in block,every block 10K bytes
            var maxCount = (int) Math.Ceiling((remaining + 0.0)/packSize); //download in block
            for (var i = 0; i < maxCount && response.IsClientConnected; i++)
            {
                response.BinaryWrite(br.ReadBytes(packSize));
                response.Flush();

                // HACK: Unexplained sleep
                var sleep = (int) Math.Ceiling(1000.0*packSize/speed); //the number of millisecond
                if (sleep > 1) Thread.Sleep(sleep);
            }
        }
    }
    return true;
}