实现效果：
页面代码：
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %> <!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"> <div> <asp:FileUpload ID="FileUpload1" runat="server" /> <asp:Button ID="Button1" runat="server" Text="上传" Width="54px" OnClick="Button1_Click" /> <asp:Label ID="Label1" runat="server" Text="" Style="color: Red"></asp:Label> <asp:Image runat="server" ID="Image1" Style="z-index: 102; left: 20px; position: absolute; top: 49px" Width="73px" /> </div> </form> </body> </html>
后台代码：
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) { } protected void Button1_Click(object sender, EventArgs e) { if (FileUpload1.FileName == "") { this.Label1.Text = "上传文件不能为空"; return; } bool fileIsValid = false; //如果确认了上传文件，则判断文件类型是否符合要求 if (this.FileUpload1.HasFile) { //获取上传文件的后缀 String fileExtension = System.IO.Path.GetExtension(this.FileUpload1.FileName).ToLower(); String[] restrictExtension = { ".gif", ".jpg", ".bmp", ".png" }; //判断文件类型是否符合要求 for (int i = 0; i < restrictExtension.Length; i++) { if (fileExtension == restrictExtension[i]) { fileIsValid = true; } //如果文件类型符合要求,调用SaveAs方法实现上传,并显示相关信息 if (fileIsValid == true) { //上传文件是否大于10M if (FileUpload1.PostedFile.ContentLength > (10 * 1024 * 1024)) { this.Label1.Text = "上传文件过大"; return; } try { //生成的文件放在那个目录下面 this.Image1.ImageUrl = "~/File/" + FileUpload1.FileName; this.FileUpload1.SaveAs(Server.MapPath("~/File/") + FileUpload1.FileName); this.Label1.Text = "文件上传成功!"; } catch { this.Label1.Text = "文件上传失败！"; } finally { } } else { this.Label1.Text = "只能够上传后缀为.gif,.jpg,.bmp,.png的文件"; } } } } }