winform:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Drawing.Drawing2D;
using System.Web;

namespace PrintLetterspacing
{

    /// <summary>
    /// 
    /// </summary>
    public partial class Form4 : Form
    {
        public string code = ""; 
        /// <summary>
        /// 
        /// </summary>
        public Form4()
        {
            InitializeComponent();
        }
        /// <summary>
        /// 
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void Form4_Load(object sender, EventArgs e)
        {
            code = CreateVerifyCode();                //取随机码

            //1.win
            System.IO.MemoryStream ms = new System.IO.MemoryStream();
            Bitmap image = this.CreateImageCode(code);
            this.pictureBox1.Image = image;


            //2.web
            //CreateImageOnPage(code, this.Context);       // 输出图片
            //Response.Cookies.Add(new HttpCookie("CheckCode", code.ToUpper()));// 使用Cookies取验证码的
        }

        /// <summary>
        /// 生成验证码
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void button1_Click(object sender, EventArgs e)
        {
            code = CreateVerifyCode();                //取随机码

            //1.win
            System.IO.MemoryStream ms = new System.IO.MemoryStream();
            Bitmap image = this.CreateImageCode(code);
            this.pictureBox1.Image = image;
        }
        /// <summary>
        /// 验证验证码
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void button2_Click(object sender, EventArgs e)
        {
            if (txtUserCode.Text.Trim().Equals(code.ToLower()))
            {
                MessageBox.Show("ok");
            }
            else
            {
                MessageBox.Show("failure");
            }  
        }

        #region 验证码长度(默认4个验证码的长度)
        int length = 4;
        public int Length
        {
            get { return length; }
            set { length = value; }
        }
        #endregion

        #region 验证码字体大小(为了显示扭曲效果，默认40像素，可以自行修改)
        int fontSize = 40;
        public int FontSize
        {
            get { return fontSize; }
            set { fontSize = value; }
        }
        #endregion

        #region 边框补(默认1像素)
        int padding = 2;
        public int Padding
        {
            get { return padding; }
            set { padding = value; }
        }
        #endregion

        #region 是否输出燥点(默认不输出)
        bool chaos = true;
        public bool Chaos
        {
            get { return chaos; }
            set { chaos = value; }
        }
        #endregion

        #region 输出燥点的颜色(默认灰色)
        Color chaosColor = Color.LightGray;
        public Color ChaosColor
        {
            get { return chaosColor; }
            set { chaosColor = value; }
        }
        #endregion

        #region 自定义背景色(默认白色)
        Color backgroundColor = Color.White;
        public Color BackgroundColor
        {
            get { return backgroundColor; }
            set { backgroundColor = value; }
        }
        #endregion

        #region 自定义随机颜色数组
        Color[] colors = { Color.Black, Color.Red, Color.DarkBlue, Color.Green, Color.Orange, Color.Brown, Color.DarkCyan, Color.Purple };
        public Color[] Colors
        {
            get { return colors; }
            set { colors = value; }
        }
        #endregion

        #region 自定义字体数组
        string[] fonts = { "Arial", "Georgia" };
        public string[] Fonts
        {
            get { return fonts; }
            set { fonts = value; }
        }
        #endregion

        #region 自定义随机码字符串序列(使用逗号分隔)
        //string codeSerial = "0,1,2,3,4,5,6,7,8,9,a,b,c,d,e,f,g,h,i,j,k,l,m,n