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 upload : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
    {

    }
protected void btupload_Click(object sender, EventArgs e)
    {
if (FileUpload1.HasFile)
        {
string filecontentType = FileUpload1.PostedFile.ContentType;
if (filecontentType == "image/bmp" || filecontentType == "image/gif" || filecontentType == "image/pjpeg" || filecontentType == "image/jpeg")
            {
string name = FileUpload1.PostedFile.FileName;
                FileInfo file= new FileInfo(name);
string filename = file.Name;
string webFilePath = Server.MapPath("image/" + filename);
if (!File.Exists(webFilePath))
                {
try
                    {
                        FileUpload1.SaveAs(webFilePath);
this.lmsg.Text = "提示：文件" + filename + "上传成功！";
this.lpathInfo.Text = "image/" + filename;
this.iPic.ImageUrl = "image/" + filename;
                    }
catch (Exception ex)
                    {
this.lmsg.Text = "提示文件上传失败，失败原因" + ex.Message;

                    }
                }
else
                {
this.lmsg.Text = "该文件已经存在！";
                }
            }
else {
this.lmsg.Text = "提示：文件类型不符";
            }
        }
    }
}

前台代码如下： <%@ Page Language="C#" AutoEventWireup="true" CodeFile="upload.aspx.cs" Inherits="upload" %>

 文件下载代码

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本文名称：文件上传后台和前台代码（文件下载也是）-创新互联
本文来源：http://kswjz.com/article/cspeio.html