今天看到了一篇不錯的文章，就拿來一起分享一下吧。
實現的是檔案的上傳與下載功能。
關於檔案上傳：
談及檔案上傳到網站上，首先我們想到的就是通過什麼上傳呢？在ASP.NET中，只需要用FileUpload控制項即可完成，但是預設上傳4M大小的資料，當然了你可以在web.config檔案中進行修改，方式如下：
<system.web> <httpRuntime executionTimeout="240" maxRequestLength="20480"/></system.web>
但是這種方式雖然可以自訂檔案的大小，但並不是無極限的修改的
下一步，現在“工具”有了,要怎麼上傳呢？按照直覺是不是應該先選中我想要上傳的檔案呢？這就對了，因為從FileUpload控制項返回後我們便已經得到了在用戶端選中的檔案的資訊了，接下來就是將這個檔案進行修改（具體的操作是：去掉所得路徑下的盤符的資訊，換成伺服器上的相關路徑下，不過這裡並沒有更改原本檔案的名稱）。然後調用相關的上傳方法就好了。
先看一下介面檔案吧
<form id="form1" runat="server"> <asp:FileUpload ID="FileUpload1" runat="server" /> <br /> <br /> <br /> <br /> <br /> <br /> <asp:ImageButton ID="ImageButton_Up" runat="server" OnClick="ImageButton_Up_Click" style="text-decoration: underline" ToolTip="Up" Width="54px" /> <asp:ImageButton ID="ImageButton_Down" runat="server" OnClick="ImageButton_Down_Click" ToolTip="Download" Width="51px" /> <br /> <br /> <asp:Label ID="Label1" runat="server" Text="Label"></asp:Label> </form>
然後是具體的邏輯
using System;using System.Collections.Generic;using System.Linq;using System.Web;using System.Web.UI;using System.Web.UI.WebControls;public partial class _Default : System.Web.UI.Page{ protected void Page_Load(object sender, EventArgs e) { } //a method for currying file updown private void UpFile() { String strFileName; //get the path of the file String FilePath = Server.MapPath("./") + "File"; //judge weather has file to upload if (FileUpload1.PostedFile.FileName != null) { strFileName = FileUpload1.PostedFile.FileName; //save all the message of the file strFileName = strFileName.Substring(strFileName.LastIndexOf("\\") + 1); try { FileUpload1.SaveAs(FilePath + "\\" + this.FileUpload1.FileName); //save the file and obey the rules Label1.Text = "Upload success!"; } catch (Exception e) { Label1.Text = "Upload Failed!"+e.Message.ToString(); } } } protected void ImageButton_Up_Click(object sender, ImageClickEventArgs e) { UpFile(); } protected void ImageButton_Down_Click(object sender, ImageClickEventArgs e) { Response.Redirect("DownFile.aspx"); }}
說完了上傳，下面談一談檔案的下載。這裡主要是藉助於Directory對象的GetFiles()方法，其可以獲得指定路徑下的所有的檔案的名稱。這樣我們就可以用之來填充一個listBox，來供我們選擇到底要下載那一個檔案。
也許這時你會有一點疑惑了，我現在知道了有哪些檔案可以下載，那下一步我要怎麼來實現呢？
其實這裡是利用了Session的儲存機制，那就是將我們在listbox 中選擇的item的內容記錄到session的特定的key中，這樣的話，我們就可以不用關心這些資訊在頁面間是怎麼傳輸的了。只需要在想要進行下載的地方直接擷取就可以了。
最為核心的是下載的過程：
if (filepathinfo.Exists) { //save the file to local Response.Clear(); Response.AddHeader("Content-Disposition", "attachment;filename=" + Server.UrlEncode(filepathinfo.Name)); Response.AddHeader("Content-length", filepathinfo.Length.ToString()); Response.ContentType = "application/octet-stream"; Response.Filter.Close(); Response.WriteFile(filepathinfo.FullName); Response.End(); }
下面看一下，下載介面的布局檔案吧
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="DownFile.aspx.cs" Inherits="DownFile" %><!DOCTYPE html><html xmlns="http://www.w3.org/1999/xhtml"><head runat="server"><meta http-equiv="Content-Type" content="text/html; charset=utf-8"/> <title></title></head><body> <form id="form1" runat="server"> <asp:ImageButton ID="ImageButton_Up" runat="server" Height="56px" OnClick="ImageButton_Up_Click" ToolTip="Upload" Width="90px" /> <asp:ImageButton ID="ImageButton_Down" runat="server" Height="52px" OnClick="ImageButton_Down_Click" style="margin-top: 0px" ToolTip="Download" Width="107px" /> <div> <asp:Label ID="Label1" runat="server" Text="Label"></asp:Label> <br /> <asp:ListBox ID="ListBox1" runat="server" Height="169px" OnSelectedIndexChanged="ListBox1_SelectedIndexChanged" Width="371px"></asp:ListBox> </div> </form></body></html>
然後是具體的邏輯代碼實現
using System;using System.Collections.Generic;using System.Linq;using System.Web;using System.Web.UI;using System.Web.UI.WebControls;using System.IO;public partial class DownFile : System.Web.UI.Page{ protected void Page_Load(object sender, EventArgs e) { if (!Page.IsPostBack)//the first time to load { //get all the file in File folder String[] AllTxt = Directory.GetFiles(Server.MapPath("File")); foreach (String name in AllTxt) { ListBox1.Items.Add(Path.GetFileName(name)); } } } protected void ListBox1_SelectedIndexChanged(object sender, EventArgs e) { //make use of sssion to save the selected file in the listbox with the key of "select" Session["select"] = ListBox1.SelectedValue.ToString(); } protected void ImageButton_Down_Click(object sender, ImageClickEventArgs e) { //judge weather user choose at least one file if (ListBox1.SelectedValue != "") { //get the path of the choosed file String FilePath = Server.MapPath("File/") + Session["select"].ToString(); //initial the object of Class FileInfo and make it as the package path FileInfo filepathinfo = new FileInfo(FilePath); //judge weather the file exists if (filepathinfo.Exists) { //save the file to local Response.Clear(); Response.AddHeader("Content-Disposition", "attachment;filename=" + Server.UrlEncode(filepathinfo.Name)); Response.AddHeader("Content-length", filepathinfo.Length.ToString()); Response.ContentType = "application/octet-stream"; Response.Filter.Close(); Response.WriteFile(filepathinfo.FullName); Response.End(); } else { Page.RegisterStartupScript("sb", "<script>alert('Please choose one file,sir!')</script>"); } } } protected void ImageButton_Up_Click(object sender, ImageClickEventArgs e) { Response.Redirect("Default.aspx"); }}
注意：
最終的上傳的檔案將會在根目錄下的File檔案夾下看到，下載的時候也是從這個檔案夾下進行下載的。
總結：
經過這個小項目的實踐，我看到了session給編程帶來的便利，也體會到了FileUpload控制項的威力；然而這並不是全部，這裡僅僅是冰山一角而已，希望大家繼續學習，一起進步一起提高！
以上就是本文的全部內容，希望對大家的學習有所協助，也希望大家多多支援雲棲社區。
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