ASP.NET实现网页版小优盘

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:

<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

<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" />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
        <asp:ImageButton ID="ImageButton_Down" runat="server" OnClick="ImageButton_Down_Click" ToolTip="Download" Width="51px" />
        <br />
        <br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
        <asp:Label ID="Label1" runat="server" Text="Label"></asp:Label>
&nbsp;
    </form>

然后是具体的逻辑

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:

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

<%@ 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" />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
        <asp:ImageButton ID="ImageButton_Down" runat="server" Height="52px" OnClick="ImageButton_Down_Click" style="margin-top: 0px" ToolTip="Download" Width="107px" />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
    <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

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。希望能和广大博友一起进步一起提高!

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