拥有网页版小U盘 ASP.NET实现文件上传与下载功能

时间:2022-09-14 18:29:13

今天看到了一篇不错的文章,就拿来一起分享一下吧。
实现的是文件的上传与下载功能。

关于文件上传:
谈及文件上传到网站上,首先我们想到的就是通过什么上传呢?在ASP.NET中,只需要用FileUpload控件即可完成,但是默认上传4M大小的数据,当然了你可以在web.config文件中进行修改,方式如下:

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<system.web>
  <httpRuntime executionTimeout="240"
    maxRequestLength="20480"/>
</system.web>

但是这种方式虽然可以自定义文件的大小,但并不是无极限的修改的

下一步,现在“工具”有了,要怎么上传呢?按照直觉是不是应该先选中我想要上传的文件呢?这就对了,因为从FileUpload控件返回后我们便已经得到了在客户端选中的文件的信息了,接下来就是将这个文件进行修改(具体的操作是:去掉所得路径下的盘符的信息,换成服务器上的相关路径下,不过这里并没有更改原本文件的名称)。然后调用相关的上传方法就好了。

先看一下界面文件吧

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<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>

然后是具体的逻辑

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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");
  }
}

说完了上传,下面谈一谈文件的下载。这里主要是借助于Directory对象的GetFiles()方法,其可以获得指定路径下的所有的文件的名称。这样我们就可以用之来填充一个listBox,来供我们选择到底要下载那一个文件。
也许这时你会有一点疑惑了,我现在知道了有哪些文件可以下载,那下一步我要怎么来实现呢?
其实这里是利用了Session的存储机制,那就是将我们在listbox 中选择的item的内容记录到session的特定的key中,这样的话,我们就可以不用关心这些信息在页面间是怎么传输的了。只需要在想要进行下载的地方直接获取就可以了。
最为核心的是下载的过程:

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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,下载界面的布局文件吧

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<%@ 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>

 然后是具体的逻辑代码实现

 

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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:
最终的上传的文件将会在根目录下的File文件夹下看到,下载的时候也是从这个文件夹下进行下载的。

总结:
经过这个小项目的实践,我看到了session给编程带来的便利,也体会到了FileUpload控件的威力;然而这并不是全部,这里仅仅是冰山一角而已,希望大家继续学习,一起进步一起提高!

以上就是本文的全部内容,希望对大家的学习有所帮助,也希望大家多多支持服务器之家。

原文链接:http://blog.csdn.net/marksinoberg/article/details/50365294