實體路徑，虛擬路徑，實體路徑與虛擬路徑轉換，檔案下載方法

1 什麼是實體路徑？什麼是虛擬路徑？
(1) 例子：
  用IIS舉個例子：  
  WEB服務類別目錄是d:\路徑  
  那麼用HTTP訪問網站根目錄的時候，其實訪問的是d:\路徑,那麼其中虛擬路徑就是\（根），實體路徑就是d:\路徑
 
(2) 我自己的理解：絕對路徑一般都是帶有磁碟完成路徑， 而虛擬路徑一般不帶有磁碟

2 程式中虛擬路徑和實體路徑的轉化

       #region 實體路徑和相對路徑的轉換
        //本地路徑轉換成URL相對路徑 
        private string urlconvertor(string imagesurl1)
        {
            string tmpRootDir = Server.MapPath(System.Web.HttpContext.Current.Request.ApplicationPath.ToString());//擷取程式根目錄
            string imagesurl2 = imagesurl1.Replace(tmpRootDir, ""); //轉換成相對路徑
            imagesurl2 = imagesurl2.Replace(@"\", @"/");
            //imagesurl2 = imagesurl2.Replace(@"Aspx_Uc/", @"");
            return imagesurl2;
        }
        //相對路徑轉換成伺服器本地實體路徑 
        private string urlconvertorlocal(string imagesurl1)
        {
            string tmpRootDir = Server.MapPath(System.Web.HttpContext.Current.Request.ApplicationPath.ToString());//擷取程式根目錄
            string imagesurl2 = tmpRootDir + imagesurl1.Replace(@"/", @"\"); //轉換成絕對路徑
            return imagesurl2;
        }
        #endregion

3 下載的方法

       /// <summary>
        /// 擷取物理地址
        /// </summary>
        public static string MapPathFile(string FileName)
        {
            return HttpContext.Current.Server.MapPath(FileName);
        }
        /// <summary>
        /// 普通下載
        /// </summary>
        /// <param name="FileName">檔案虛擬路徑</param>
        public static bool DownLoadold(string FileName)
        {
            bool bools = false;
            string destFileName = MapPathFile(FileName);
            if (File.Exists(destFileName))
            {
                FileInfo fi = new FileInfo(destFileName);
                HttpContext.Current.Response.Clear();
                HttpContext.Current.Response.ClearHeaders();
                HttpContext.Current.Response.Buffer = false;
                HttpContext.Current.Response.AppendHeader("Content-Disposition", "attachment;filename=" + HttpUtility.UrlEncode(Path.GetFileName(destFileName), System.Text.Encoding.UTF8));
                HttpContext.Current.Response.AppendHeader("Content-Length", fi.Length.ToString());
                HttpContext.Current.Response.ContentType = "application/octet-stream";
                HttpContext.Current.Response.WriteFile(destFileName);
                HttpContext.Current.Response.Flush();
                HttpContext.Current.Response.End();
                bools = true;
            }
            return bools;
        }

        public static void ResponseFile(string path, HttpContext context)
        {
            context = HttpContext.Current;

            System.IO.Stream iStream = null;
            byte[] buffer = new Byte[10000];
            int length;
            long dataToRead;
            string filename = System.IO.Path.GetFileName(path);

            try
            {
                iStream = new System.IO.FileStream(path, System.IO.FileMode.Open, System.IO.FileAccess.Read, System.IO.FileShare.Read);
                dataToRead = iStream.Length;
                context.Response.ContentType = "application/octet-stream";
                context.Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(filename, System.Text.Encoding.UTF8));

                while (dataToRead > 0)
                {
                    if (context.Response.IsClientConnected)
                    {
                        length = iStream.Read(buffer, 0, 10000);
                        context.Response.OutputStream.Write(buffer, 0, length);
                        context.Response.Flush();

                        buffer = new Byte[10000];
                        dataToRead = dataToRead - length;
                    }
                    else
                    {
                        dataToRead = -1;
                    }
                }
            }
            catch (Exception ex)
            {
                context.Response.Write(ex.Message);
            }
            finally
            {
                if (iStream != null)
                {
                    iStream.Close();
                }
            }
        }

        public static void ResponseFile(string path, string fileName, HttpContext context)
        {
            context = HttpContext.Current;

            System.IO.Stream iStream = null;
            byte[] buffer = new Byte[10000];
            int length;
            long dataToRead;

            try
            {
                iStream = new System.IO.FileStream(path, System.IO.FileMode.Open, System.IO.FileAccess.Read, System.IO.FileShare.Read);
                dataToRead = iStream.Length;
                context.Response.ContentType = "application/octet-stream";
                context.Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(fileName, System.Text.Encoding.UTF8));

                while (dataToRead > 0)
                {
                    if (context.Response.IsClientConnected)
                    {
                        length = iStream.Read(buffer, 0, 10000);
                        context.Response.OutputStream.Write(buffer, 0, length);
                        context.Response.Flush();

                        buffer = new Byte[10000];
                        dataToRead = dataToRead - length;
                    }
                    else
                    {
                        dataToRead = -1;
                    }
                }
            }
            catch (Exception ex)
            {
                context.Response.Write(ex.Message);
            }
            finally
            {
                if (iStream != null)
                {
                    iStream.Close();
                }
            }
        }