%@ Page Language="C#" AutoEventWireup="true" CodeBehind="UploadPic.aspx.cs" Inherits="Pic_Try.UploadPic" %>

!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

html xmlns="http://www.w3.org/1999/xhtml">
head runat="server">
 title>图片上传和显示/title>
 style type="text/css">
 .pic_text{ color:Red;}
 .pic_label { color:Gray; margin-top:5px; margin-bottom:5px;}
 .pic_image { margin:5px;}
 /style>
/head>
body>
 form id="form1" runat="server">
 div class="pic_image">asp:Image ID="pic" runat="server" />/div>
 div>asp:FileUpload ID="pic_upload" runat="server" />asp:Label ID="lbl_pic" runat="server" class="pic_text">/asp:Label>/div>
 div class="pic_label">上传图片格式为.jpg, .gif, .bmp,.png,图片大小不得超过8M/div>
 div>asp:Button ID="btn_upload" runat="server" Text="上传" onclick="btn_upload_Click"/>/div>
 /form>
 
/body>
/html>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.IO;
using System.Security.Cryptography;
using System.Web.Security;

namespace Pic_Try
{
 public partial class UploadPic : System.Web.UI.Page
 {
 protected void Page_Load(object sender, EventArgs e)
 {

 }

 protected void btn_upload_Click(object sender, EventArgs e)
 {
  Boolean fileOk = false;
  if (pic_upload.HasFile)//验证是否包含文件
  {
  //取得文件的扩展名,并转换成小写
  string fileExtension = Path.GetExtension(pic_upload.FileName).ToLower();
  //验证上传文件是否图片格式
  fileOk = IsImage(fileExtension);

  if (fileOk)
  {
   //对上传文件的大小进行检测，限定文件最大不超过8M
   if (pic_upload.PostedFile.ContentLength  8192000)
   {
   string filepath = "/images/";
   if (Directory.Exists(Server.MapPath(filepath)) == false)//如果不存在就创建file文件夹
   {
    Directory.CreateDirectory(Server.MapPath(filepath));
   }
   string virpath = filepath + CreatePasswordHash(pic_upload.FileName, 4) + fileExtension;//这是存到服务器上的虚拟路径
   string mappath = Server.MapPath(virpath);//转换成服务器上的物理路径
   pic_upload.PostedFile.SaveAs(mappath);//保存图片
   //显示图片
   pic.ImageUrl = virpath;
   //清空提示
   lbl_pic.Text = "";
   }
   else {
   pic.ImageUrl = "";
   lbl_pic.Text = "文件大小超出8M！请重新选择！";
   }
  }
  else {
   pic.ImageUrl = "";
   lbl_pic.Text = "要上传的文件类型不对！请重新选择！";
  }
  }
  else
  {
  pic.ImageUrl = "";
  lbl_pic.Text = "请选择要上传的图片！";
  }
 }

 /// summary>
 /// 验证是否指定的图片格式
 /// /summary>
 /// param name="str">/param>
 /// returns>/returns>
 public bool IsImage(string str) {
  bool isimage = false;
  string thestr = str.ToLower();
  //限定只能上传jpg和gif图片
  string[] allowExtension = { ".jpg", ".gif", ".bmp",".png" };
  //对上传的文件的类型进行一个个匹对
  for (int i = 0; i  allowExtension.Length; i++)
  {
  if (thestr == allowExtension[i])
  {
   isimage = true;
   break;
  }
  }
  return isimage;
 }

 /// summary>
 /// 创建一个指定长度的随机salt值
 /// /summary>
 public string CreateSalt(int saltLenght)
 {
  //生成一个加密的随机数
  RNGCryptoServiceProvider rng = new RNGCryptoServiceProvider();
  byte[] buff = new byte[saltLenght];
  rng.GetBytes(buff);
  //返回一个Base64随机数的字符串
  return Convert.ToBase64String(buff);
 }

 
 /// summary>
 /// 返回加密后的字符串
 /// /summary>
 public string CreatePasswordHash(string pwd, int saltLenght)
 {
  string strSalt = CreateSalt(saltLenght);
  //把密码和Salt连起来
  string saltAndPwd = String.Concat(pwd, strSalt);
  //对密码进行哈希
  string hashenPwd = FormsAuthentication.HashPasswordForStoringInConfigFile(saltAndPwd, "sha1");
  //转为小写字符并截取前16个字符串
  hashenPwd = hashenPwd.ToLower().Substring(0, 16);
  //返回哈希后的值
  return hashenPwd;
 }
 }
}

?xml version="1.0" encoding="utf-8"?>

!--
 如何配置 ASP.NET 应用程序的详细消息
 -->

configuration>
 system.web>
 compilation debug="true" targetFramework="4.0" />
 httpRuntime executionTimeout="240" maxRequestLength="8192000"/>
 /system.web>

/configuration>