C# 生成简单验证码

网站登录总是会用到验证码，生成验证码对于C#来说很简单。因为有专门封装好的GDI+类可以直接调用使用具体代码如下

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

namespace Ajax.验证码
{
    public partial class Yanma : System.Web.UI.Page
    {
        private int CodeNum = 4;
        private string codeNum = "";
        protected void Page_Load(object sender, EventArgs e)
        {
            VeriflcationCode();
            HuaCode(codeNum);
        }

        private void VeriflcationCode()
        {
            //生成验证码
            string AllChar = "1,2,3,4,5,6,7,8,9,0,A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,W,X,Y,Z";
            string[] StrChar = AllChar.Split(',');
            Random rd = new Random();
            string Codes = "";
            for (int i = 0; i < CodeNum; i++)
            {
                Codes += StrChar[rd.Next(0, 35)];
            }
            codeNum = Codes;
            Session["VerCode"] = Codes; 
        }

        private void HuaCode(string Codes)
        {
            int iwidth = (int)(Codes.Length * 17);//定义画布的宽
            System.Drawing.Bitmap images = new System.Drawing.Bitmap(iwidth, 25);//声明一个画布类，初始化图片的宽和高

            Graphics g = Graphics.FromImage(images);
            Font f = new Font("Arial", 14);//定义文字类型
            Brush b = new System.Drawing.SolidBrush(Color.Black);//文字颜色 黑色
            Brush r = new System.Drawing.SolidBrush(Color.FromArgb(166, 8, 8));//文字颜色 
            g.Clear(System.Drawing.ColorTranslator.FromHtml("#99C1CB"));//背景色

            char[] ch = Codes.ToCharArray();
            for (int i = 0; i < ch.Length; i++)
            {
                if (ch[i] >= '0' && ch[i] <= '9')
                {
                    //数字用红色显示 
                    g.DrawString(ch[i].ToString(), f, r, 3 + (i * 14), 3);//将文字画出 文字、字体类型、字体颜色、字体间距、字体于顶部间距
                }
                else
                {   //字母用黑色显示
                    g.DrawString(ch[i].ToString(), f, b, 3 + (i * 14), 3);
                }
            }

            //for循环用来生成一些随机的水平线
            Pen blackPen = new Pen(Color.Black, 0);
            Random rand = new Random();
            for (int i = 0; i < 5; i++)
            {
                int y = rand.Next(images.Height);
                g.DrawLine(blackPen, 0, y, images.Width, y);
            }


            System.IO.MemoryStream ms = new System.IO.MemoryStream();
            images.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
            //history back 不重复 
            Response.Cache.SetNoStore();//这一句         
            Response.ClearContent();
            Response.ContentType = "image/Jpeg";
            Response.BinaryWrite(ms.ToArray());
            g.Dispose();
            images.Dispose();
        }

效果为：