物理路径，虚拟路径，物理路径与虚拟路径转换，文件下载方法

1 什么是物理路径？什么是虚拟路径？
(1) 例子：
  用IIS举个例子：   
  WEB服务目录是d:\路径   
  那么用HTTP访问网站根目录的时候，其实访问的是d:\路径,那么其中虚拟路径就是\（根），物理路径就是d:\路径 
 
(2) 我自己的理解：绝对路径一般都是带有磁盘完成路径， 而虚拟路径一般不带有磁盘

2 程序中虚拟路径和物理路径的转化

       #region 物理路径和相对路径的转换
        //本地路径转换成URL相对路径  
        private string urlconvertor(string imagesurl1)
        {
            string tmpRootDir = Server.MapPath(System.Web.HttpContext.Current.Request.ApplicationPath.ToString());//获取程序根目录
            string imagesurl2 = imagesurl1.Replace(tmpRootDir, ""); //转换成相对路径
            imagesurl2 = imagesurl2.Replace(@"\", @"/");
            //imagesurl2 = imagesurl2.Replace(@"Aspx_Uc/", @"");
            return imagesurl2;
        }
        //相对路径转换成服务器本地物理路径  
        private string urlconvertorlocal(string imagesurl1)
        {
            string tmpRootDir = Server.MapPath(System.Web.HttpContext.Current.Request.ApplicationPath.ToString());//获取程序根目录 
            string imagesurl2 = tmpRootDir + imagesurl1.Replace(@"/", @"\"); //转换成绝对路径 
            return imagesurl2;
        }
        #endregion

3 下载的方法

       /// <summary>
        /// 获取物理地址
        /// </summary>
        public static string MapPathFile(string FileName)
        {
            return HttpContext.Current.Server.MapPath(FileName);
        }
        /// <summary>
        /// 普通下载
        /// </summary>
        /// <param name="FileName">文件虚拟路径</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();
                }
            }
        }