if(File1.PostedFile.ContentLength>0)

 如果用户有上传的文件，则：

string name = File1.PostedFile.FileName ;//获取输入的文件名字

     int i= name.LastIndexOf(".") ;

     string newname =name.Substring(i) ;//获取文件的扩展名

     //改变下面的“c:\\"到你想要保存的地址。

     DateTime now=DateTime.Now;

     string strname=now.Year.ToString()+now.Month.ToString()+now.Day.ToString()+File1.PostedFile.ContentLength.ToString()+newname;//对文件进行重命名。名字为：年+月+日+文件大小。

asp.net下载文件的常用方法大全(转)

1.流方式下载     protected void Button4_Click(object sender, EventArgs e)     {         string fileName = "aaa.txt";//客户端保存的文件名         string filePath = Server.MapPath("DownLoad/aaa.txt");//路径

        //以字符流的形式下载文件         FileStream fs = new FileStream(filePath, FileMode.Open);         byte[] bytes = new byte[(int)fs.Length];         fs.Read(bytes, 0, bytes.Length);         fs.Close();         Response.ContentType = "application/octet-stream";         //通知浏览器下载文件而不是打开         Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(fileName, System.Text.Encoding.UTF8));         Response.BinaryWrite(bytes);         Response.Flush();         Response.End();

    }

   2.WriteFile分块下载     protected void Button3_Click(object sender, EventArgs e)     {

        string fileName = "aaa.txt";//客户端保存的文件名         string filePath = Server.MapPath("DownLoad/aaa.txt");//路径

        System.IO.FileInfo fileInfo = new System.IO.FileInfo(filePath);

        if (fileInfo.Exists == true)         {             const long ChunkSize = 102400;//100K 每次读取文件，只读取100Ｋ，这样可以缓解服务器的压力             byte[] buffer = new byte[ChunkSize];

            Response.Clear();             System.IO.FileStream iStream = System.IO.File.OpenRead(filePath);             long dataLengthToRead = iStream.Length;//获取下载的文件总大小             Response.ContentType = "application/octet-stream";             Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(fileName));             while (dataLengthToRead > 0 && Response.IsClientConnected)             {                 int lengthRead = iStream.Read(buffer, 0, Convert.ToInt32(ChunkSize));//读取的大小                 Response.OutputStream.Write(buffer, 0, lengthRead);                 Response.Flush();                 dataLengthToRead = dataLengthToRead - lengthRead;             }             Response.Close();         }     }

   3.WriteFile实现下载     protected void Button2_Click(object sender, EventArgs e)     {         /*          using System.IO;                   */

        string fileName = "asd.txt";//客户端保存的文件名         string filePath = Server.MapPath("DownLoad/aaa.txt");//路径

        FileInfo fileInfo = new FileInfo(filePath);         Response.Clear();         Response.ClearContent();         Response.ClearHeaders();         Response.AddHeader("Content-Disposition", "attachment;filename=" + fileName);         Response.AddHeader("Content-Length", fileInfo.Length.ToString());         Response.AddHeader("Content-Transfer-Encoding", "binary");         Response.ContentType = "application/octet-stream";         Response.ContentEncoding = System.Text.Encoding.GetEncoding("gb2312");         Response.WriteFile(fileInfo.FullName);         Response.Flush();         Response.End();     }

   4.TransmitFile实现下载          protected void Button1_Click1(object sender, EventArgs e)         {             /*              微软为Response对象提供了一个新的方法TransmitFile来解决使用Response.BinaryWrite              下载超过400mb的文件时导致Aspnet_wp.exe进程回收而无法成功下载的问题。              代码如下：              */             string strFileName = "三部闲置设备管理系统操作手册IEMS.ppt";             Response.ContentType = "application/x-zip-compressed";             //Response.ContentEncoding = System.Text.Encoding.GetEncoding("gb2312");             string filename = BLL.Config.PART_EM_UPLOAD_DOC + strFileName;

            //BLL.Config.PART_EM_UPLOAD_DOC 为路径   ("D:/EMUploadDoc/" )             Response.AddHeader("Content-Disposition", "attachment;filename=" +Server.UrlPathEncode(strFileName));

           //Server.UrlPathEncode()解决文件名的乱码问题.                         Response.TransmitFile(filename);         }

 上传文件实例：

if (Fileupload.PostedFile.ContentLength > 0)    //判断用户是否上传了文件                 {                     string strfilename = Fileupload.PostedFile.FileName;  //获取上传的路径及文件名                     int i = strfilename.IndexOf(".");

    // if (!System.IO.Directory.Exists(path)) Directory.CreateDirectory(path); 判断是否有上传的目录没有则创建此目录                     string strnewname = strfilename.Substring(i); //获取上传文件的扩展名                     DateTime dtTime = new DateTime();                     string struploadname = Fileupload.FileName; //获取上传文件的文件名                     //string struploadname = DateTime.Now.ToString("yyyyMMddhhmmss")                     //             + Fileupload.PostedFile.ContentLength.ToString() + strnewname;   //对文件进行重命名。名字为：年+月+日+文件大小                     String path = Server.MapPath("~/FileUpload/ReceptionDataBase/");   //获取服务器文件夹                     string fileurl = path + "\\" + struploadname;                     Fileupload.PostedFile.SaveAs(fileurl);    //将文件上传至服务器                     resources.UploadFile = struploadname;   //附件文件名

         }

下载文件实例：

首先引用using System.IO;

 if (!string.IsNullOrEmpty(this.FileName))   //判断是否有附件，从资料库读取附件名称FileName表示附件名称             {                 string filename = this.FileName;                 string filepath = "~/FileUpload/ReceptionDataBase/" + filename;                 string path = Server.MapPath(filepath);  //获取文件路径

                FileStream fs = new FileStream(path, FileMode.Open);                 byte[] bytes = new byte[(int)fs.Length];                 fs.Read(bytes, 0, bytes.Length);                 fs.Close();                 Response.ContentType = "application/octet-stream";                 //通知浏览器下载文件不是打开文件                 Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(filename, System.Text.Encoding.UTF8));                 Response.TransmitFile(path);                 Response.BinaryWrite(bytes);                 Response.Flush();                 Response.End();

       //测试时不能用下载软件（迅雷等）下载符件             }             else             {                 this.ClientScriptAlert("此项目没有附件！");             }             this.FileName = "";