C# ASP 上传/下载文件

1.  上传文件前台页面

            <div style="padding-left:20px;">
                <asp:FileUpload ID="FileUpload1" runat="server" style="width:400px;"/>
                <asp:Button ID="Button1" runat="server" OnClick="Upload_Click" Text="上传" style="width:65px;height:22px"></asp:Button >
             </div>

　　上传文件后台代码

     private string _directory = @"../Questionnaire35"; 

     protected void Upload_Click(object sender, EventArgs e)
     {
         try
         {
             if (Request.Files.Count > )
             {
                 if (string.IsNullOrEmpty(Request.Files[].FileName))
                 {
                     return;
                 }
                 //判断文件大小
                 int length = Request.Files[].ContentLength;
                 if (length > )
                 {
                     Page.ClientScript.RegisterStartupScript(this.GetType(), "alert", "<script>alert('文件大于1M，不能上传');</script>");
                     return;
                 }

                 string type = Request.Files[].ContentType;
                 string fileExt = Path.GetExtension(Request.Files[].FileName).ToLower();
                 //只能上传图片，过滤不可上传的文件类型
                 string fileFilt = ".xlsx|.xls|.docx|.doc|......";
                 if (fileFilt.IndexOf(fileExt) <= -)
                 {
                     Page.ClientScript.RegisterStartupScript(this.GetType(), "alert", "<script>alert('只能上传文档');</script>");
                     return;
                 }
                 else
                 {
                     UserInfo user = (UserInfo)Session["UserInfo"];
                     //string fileName = Server.MapPath(_directory) + "\\" + DateTime.Now.ToString("yyyyMMddHHmmssfff") + fileExt;
                     string fileName = Server.MapPath(_directory) + "\\" + user.Pkid + fileExt;
                     Request.Files[].SaveAs(fileName);
                     Page.ClientScript.RegisterStartupScript(this.GetType(), "alert", "<script>alert('上传成功');</script>");
                     Answer answer = (Answer)Session["Answer"];
                     answer.Answer35 = "done";
                 }
             }
         }
         catch
         {
             throw new Exception();
         }
     }

　　需要引入 using System.IO;

2. 下载文件前台页面

 <asp:LinkButton runat="server" ID="DownLoadQuestionnaire" Text="下载文件" OnClick="DownLoadQuestionnaire_Click" />

下载文件后台代码

     protected void DownLoadQuestionnaire_Click(object sender, EventArgs e)
     {
         Response.ContentType = "application/x-zip-compressed";

         string docName = "中高职衔接院校调研问卷.docx"; //文件路径
         docName = HttpUtility.UrlEncode(docName, System.Text.Encoding.UTF8);
         Response.AddHeader("Content-Disposition", "attachment;filename=" + docName);
         string filename = Server.MapPath("DownLoad/中高职衔接院校调研问卷.docx");
         //指定编码 防止中文文件名乱码
         Response.HeaderEncoding = System.Text.Encoding.GetEncoding("GB2312");
         Response.TransmitFile(filename);

     }

　　值得注意的就是文件名设置一下编码，不然出现下载时文件名乱码：

　　HttpUtility.UrlEncode(docName, System.Text.Encoding.UTF8);

　　据说还有很多种下载方式，没一个一个的试验：

     protected void DownLoadQuestionnaire_Click(object sender, EventArgs e)
     {
         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();

     }

     protected void DownLoadQuestionnaire_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 = ;//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 >  && Response.IsClientConnected)
             {
                 int lengthRead = iStream.Read(buffer, , Convert.ToInt32(ChunkSize));//读取的大小
                 Response.OutputStream.Write(buffer, , lengthRead);
                 Response.Flush();
                 dataLengthToRead = dataLengthToRead - lengthRead;
             }
             Response.Close();
         }
     }

     protected void DownLoadQuestionnaire_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, , 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();
     }