c#生成图片验证码

一般处理程序 ashx :它没有服务器控件，用response输出什么就是什么，一般作为文件来使用，放在aspx页面里使用

session:是用来存储数据的，设计一个服务器端的全局变量，在一般处理程序中，使用session需要引用命名空间，并继承接口

imagebutton用来显示验证码图片，通过?id=...来改变图片

一般处理程序ashx里的代码

<%@ WebHandler Language="C#" Class="Handler" %>

using System;
using System.Web;
using System.Drawing;
using System.Web.SessionState;
//引用的命名空间  
public class Handler : IHttpHandler, IRequiresSessionState
{
    public string charSet = "2,3,4,5,6,8,9,A,B,C,D,E,F,G,H,J,K,M,N,P,R,S,U,W,X,Y";
    public void ProcessRequest (HttpContext context)
    {
       
            string validateCode = CreateRandomCode(4);
            context.Session["ValidateCode"] = validateCode;
           CreateImage(validateCode, context);  
        
        //context.Response.ContentType = "text/plain";
        //context.Response.Write("Hello World");
        //string validateCode = CreateRandomCode(4);
        //context.Session["ValidateCode"] = validateCode;
        //CreateImage(validateCode, context);   

    }
 
    public bool IsReusable
    {
        get
        {
            return false;
        }
    }

    private string CreateRandomCode(int n)
    {
        string[] CharArray = charSet.Split(',');
        string randomCode = "";
        int temp = -1;
        Random rand = new Random();
        for (int i = 0; i < n; i++)
        {
            if (temp != -1)
            {
                rand = new Random(i * temp * ((int)DateTime.Now.Ticks));
            } int t = rand.Next(CharArray.Length - 1);
            if (temp == t)
            {
                return CreateRandomCode(n);
            } temp = t;
            randomCode += CharArray[t];
        }
        return randomCode;
    }


    //绘制验证码图片
    private void CreateImage(string checkCode, HttpContext context)
    {
        int iwidth = (int)(checkCode.Length * 13);
        System.Drawing.Bitmap image = new System.Drawing.Bitmap(iwidth, 23);
        Graphics g = Graphics.FromImage(image);
        Font f = new System.Drawing.Font("Arial", 12, (System.Drawing.FontStyle.Italic | System.Drawing.FontStyle.Bold));        // 前景色  

        Brush b = new System.Drawing.SolidBrush(Color.Black);        // 背景色       
        g.Clear(Color.White);        // 填充文字        
        g.DrawString(checkCode, f, b, 0, 1);        // 随机线条        
        Pen linePen = new Pen(Color.Gray, 0);
        Random rand = new Random();
        for (int i = 0; i < 5; i++)
        {
            int x1 = rand.Next(image.Width);
            int y1 = rand.Next(image.Height);
            int x2 = rand.Next(image.Width);
            int y2 = rand.Next(image.Height);
            g.DrawLine(linePen, x1, y1, x2, y2);
        }
        // 随机点        
        for (int i = 0; i < 30; i++)
        {
            int x = rand.Next(image.Width);
            int y = rand.Next(image.Height);
            image.SetPixel(x, y, Color.Gray);
        }
        // 边框       
        g.DrawRectangle(new Pen(Color.Gray), 0, 0, image.Width - 1, image.Height - 1);
        // 输出图片  
        System.IO.MemoryStream ms = new System.IO.MemoryStream();
        image.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
        context.Response.ClearContent();
        context.Response.ContentType = "image/Jpeg";
        context.Response.BinaryWrite(ms.ToArray());

        g.Dispose();
        image.Dispose();
    }    


}

aspx里的代码

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Drawing;
using System.IO;


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 (TextBox1.Text.ToUpper().Trim() == Session["ValidateCode"].ToString().ToUpper().Trim())
        {
           Response.Write("<script>alert('验证码相同')</script>");
        }
else
{
   Response.Write("<script>alert('验证码不正确')</script>");
}


}
    //看不清，换一张
protected void Button2_Click(object sender, EventArgs e)
{
    //通过超链接传值来改变验证码图片
    ImageButton1.ImageUrl = "Handler.ashx?id="+new Random().Next(62);
}
}

aspx界面里的代码

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>

<!DOCTYPE html>
<script runat="server">

   
   
</script>


<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>
    
        <br />
        <asp:ScriptManager ID="ScriptManager1" runat="server">
        </asp:ScriptManager>
        <asp:Button ID="Button1" runat="server" OnClick="Button1_Click" Text="登录" />
    
        <br />
        <br />
&nbsp;<br />
&nbsp;&nbsp;
        <asp:Label ID="Label1" runat="server" Text="验证码"></asp:Label>
&nbsp;&nbsp;
        <asp:TextBox ID="TextBox1" runat="server" Height="32px"></asp:TextBox>
&nbsp;&nbsp;&nbsp;&nbsp;<asp:UpdatePanel ID="UpdatePanel1" runat="server">
            <ContentTemplate>
                <asp:Button ID="Button2" runat="server" OnClick="Button2_Click" Text="看不清 换一张" />



                重点看这一句
               <asp:ImageButton ID="ImageButton1" runat="server" ImageUrl="Handler.ashx" />



            </ContentTemplate>
        </asp:UpdatePanel>
&nbsp;&nbsp;&nbsp;&nbsp
        &nbsp;
 
 

       
        <br />
        <br />
        <br />
        <br />
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
            
    </div>
    </form>
</body>
</html>