Webfrom --图片验证码

(一) 添加一个一般处理程序，

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

using System;
using System.Web;
using System.Drawing;//引用
using System.Web.SessionState;//IRequiresSessionState的命名空间

public class show : IHttpHandler, IRequiresSessionState
{

    public void ProcessRequest(HttpContext context)
    {
        context.Response.ContentType = "image/jpeg";//要输出的类型

        Bitmap img = new Bitmap(50, 20);//造空白图
        Graphics gr = Graphics.FromImage(img);//往哪个图上去绘制
        Font font = new Font("宋体", 12, FontStyle.Bold);//设置字体
        SolidBrush brush = new SolidBrush(Color.White);//设置刷子
        gr.FillRectangle(brush, 0, 0, 50, 20);//刷子绘制的形状
        brush.Color = Color.Red;//颜色

        string s = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
        string str = "";
        Random rand = new Random();//初始化随机数
        for (int i = 0; i < 4; i++)
        {
            int start = rand.Next(62); //生成一个随机的起始位置
            str += s.Substring(start, 1).ToString();
        }
        //需要继承接口
        context.Session["yanzheng"] = str;
        gr.DrawString(str, font, brush, 0, 0);//绘制完了图片了
        //将图片保存，通过response响应流保存
        img.Save(context.Response.OutputStream, System.Drawing.Imaging.ImageFormat.Jpeg);
    }

    public bool IsReusable
    {
        get
        {
            return false;
        }
    }

}

（二）制作一个主页面 Default

添加一个imagebutton , textbox ,button

不要忘记在imageUrl中添加写的图片的方法。

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)
    {
        string txtyanzheng = TextBox1.Text;
        if (string.IsNullOrWhiteSpace(txtyanzheng))
        {

        }
        else
        {
            string yanzheng = Session["yanzheng"].ToString();  //用Session传值接收过来

            if (txtyanzheng == yanzheng)
            {
                Response.Write("<script>alert('注册成功')</script>");
            }
            else
            {
                Response.Write("<script>alert('验证码不正确')</script>");
            }
        }
    }
    
 
}

效果图：