C#-WebForm-★ 制作图片验证码 ★

在前台放在如下四个控件

<div>
        <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>　　　　　　　<%--TextBox-等待输入验证码--%>
        <asp:Image ID="Image1" runat="server" ImageUrl="YZM.aspx" />　　　　 <%--Image-显示验证码图片--%>
        <asp:Button ID="Button1" runat="server" Text="提交验证" />　　　　　　 <%--Button-提交进行验证--%>
        <asp:Label ID="Label1" runat="server" Text="验证中..."></asp:Label>　　 <%--Label-显示验证结果--%>
    </div>

此时验证码为空，不显示任何东西

步骤：

一、给验证码图片控件加一个连接，此连接是.aspx网页，此网页不需要前台，只需要打开时后台做一个验证码图片展示出来即可

<asp:Image ID="Image1" runat="server" ImageUrl="YZM.aspx" />

二、在YZM.aspx后台中制作简单验证码

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

public partial class YZM : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        Random r = new Random();

        //制作“位图”（指定长宽的矩形区域）
        Bitmap img = new Bitmap(60,30);

        //准备制作-
        //设定画布
        Graphics g = Graphics.FromImage(img);
        //输出的字符串
        string all = "abcdefghijklmnopqrstuvwsyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
        string s = "";
        for (int i = 1; i <= 4; i++)
        {
            s += all.Substring(r.Next(all.Length),1);
        }
        //字符串的字体
        Font f=new Font ("微软雅黑",16);
        //字体的颜色
        Brush b=new SolidBrush(Color.Red);
        //起始位置
        PointF p=new PointF (3,3);
        //进行制作-
        g.DrawString(s, f, b, p);

        //进行保存(保存到流中)
        img.Save(Response.OutputStream,System.Drawing.Imaging.ImageFormat.Png);
        Response.End();
    }
}

效果：

三、设置<提交验证>功能

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)
    {
        btn_verification.Click+=btn_verification_Click;
    }
    //<提交验证>按钮点击事件
    void btn_verification_Click(object sender, EventArgs e)
    {
        string s1 = txt_userYZM.Text;
        string s2 = Session["YZM"].ToString();
        if (s1.ToUpper() == s2.ToUpper())
        {
            Label1.Text = "验证成功！";
        }
        else
        {
            Label1.Text = "验证失败！";
        }
    }
}

效果：

验证成功自动刷新

四、设置点击验证码切换验证码 - 前端JS

<script type="text/javascript">
    var a = 0;
    document.getElementById("Image1").onclick = function () {
        this.setAttribute("src", "yzm.aspx?id=" + a);
        a++;
    }
</script>

五、设置验证码背景色和干扰线　　填充矩形区域：FillRectangle

//设定背景色
        g.FillRectangle(new SolidBrush(clist[r.Next(clist.Count)]), 0, 0, 70, 30);

        //设置干扰线
        for (int i = 1; i <= 10; i++)
        {
            //随机颜色
            Color c_line = clist[r.Next(0, clist.Count)];
            //干扰线颜色、粗细
            Pen p_line = new Pen(new SolidBrush(c_line), r.Next(1, 5));
            //画干扰线
            g.DrawLine(p_line, new PointF(r.Next(0, 70), r.Next(0, 30)), new PointF(r.Next(0, 70), r.Next(0, 30)));
        }

===========================================

验证码图片后台代码：

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

public partial class YZM : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        Random r = new Random();
        //颜色集合
        List<Color> clist = new List<Color>();
        clist.Add(Color.Yellow);
        clist.Add(Color.Pink);
        clist.Add(Color.Blue);
        clist.Add(Color.Green);
        clist.Add(Color.Orange);
        clist.Add(Color.Black);

        //制作“位图”（指定长宽的矩形区域）
        Bitmap img = new Bitmap(70, 30);

        //设定画布
        Graphics g = Graphics.FromImage(img);

        //设定背景色
        g.FillRectangle(new SolidBrush(clist[r.Next(clist.Count)]), 0, 0, 70, 30);

        //设置干扰线
        for (int i = 1; i <= 10; i++)
        {
            //随机颜色
            Color c_line = clist[r.Next(0, clist.Count)];
            //干扰线颜色、粗细
            Pen p_line = new Pen(new SolidBrush(c_line), r.Next(1, 5));
            //画干扰线
            g.DrawLine(p_line, new PointF(r.Next(0, 70), r.Next(0, 30)), new PointF(r.Next(0, 70), r.Next(0, 30)));
        }

        //输出的字符串
        string all = "abcdefghijklmnopqrstuvwsyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
        string s = "";
        for (int i = 1; i <= 4; i++)
        {
            s += all.Substring(r.Next(all.Length), 1);
        }
        //生成的验证码放入全局变量中
        Session["YZM"] = s;
        //字符串的字体
        Font f = new Font("微软雅黑", 16);
        //字体的颜色
        Brush b = new SolidBrush(Color.Red);
        //起始位置
        PointF p = new PointF(3, 3);
        //进行制作-
        g.DrawString(s, f, b, p);

        //进行保存(保存到流中)
        img.Save(Response.OutputStream, System.Drawing.Imaging.ImageFormat.Png);
        Response.End();
    }
}