.Net验证码

写了个验证码小程序，代码贴上，要的自己拿去用

using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Drawing;

namespace SessionCode
{
    public partial class checkimage : System.Web.UI.Page
    {
        /// <summary>
        /// 验证码产生程序
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        protected void Page_Load(object sender, EventArgs e)
        {
            GetCode();
        }

        //产生code
        protected void GetCode()
        {
            System.Random rand = new Random();
            int len = 4;    //这里设置验证码长度，我的定义为4，最近见到些网上上有随机4，5，6位的。这里自己写个随机函数就可以了。
            char[] chars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ".ToCharArray();
            System.Text.StringBuilder myStr = new System.Text.StringBuilder();

            for (int iCount = 0; iCount < len; iCount++)
            {
                myStr.Append(chars[rand.Next(chars.Length)]);
            }
            string text = myStr.ToString();
            // 保存验证码到 session 中以便其他模块使用
            Session["code"] = text;   //这里你的登陆页面判断输入验证码是否正确，if (txtCode.text == Session["code"]) 正确读库检索User/Password,不正确弹窗。自己写
            Size ImageSize = Size.Empty;
            Font myFont = new Font("MS Sans Serif", 12);  //绘制在验证图片上的文字大小
            // 计算验证码图片大小
            using (Bitmap bmp = new Bitmap(5, 5))
            {
                using (Graphics g = Graphics.FromImage(bmp))
                {
                    SizeF size = g.MeasureString(text, myFont, 10000);
                    ImageSize.Width = (int)size.Width + 3;
                    ImageSize.Height = (int)size.Height + 3;
                }
            }
            // 创建验证码图片
            using (Bitmap bmp = new Bitmap(ImageSize.Width, ImageSize.Height))
            {
                // 绘制验证码文本
                using (Graphics g = Graphics.FromImage(bmp))
                {
                    g.Clear(Color.White);
                    using (StringFormat f = new StringFormat())
                    {
                        f.Alignment = StringAlignment.Near;
                        f.LineAlignment = StringAlignment.Center;
                        f.FormatFlags = StringFormatFlags.NoWrap;
                        g.DrawString(text, myFont, Brushes.Black, new RectangleF(0, 0, ImageSize.Width, ImageSize.Height), f);
                    }//using
                }//using
                // 制造杂点 杂点面积占图片面积的 20%
                int num = ImageSize.Width * ImageSize.Height * 20 / 100;
                for (int iCount = 0; iCount < num; iCount++)
                {
                    // 在随机的位置使用随机的颜色设置图片的像素
                    int x = rand.Next(ImageSize.Width);
                    int y = rand.Next(ImageSize.Height);
                    int r = rand.Next(255);
                    int g = rand.Next(255);
                    int b = rand.Next(255);
                    Color c = Color.FromArgb(r, g, b);
                    bmp.SetPixel(x, y, c);
                }//for
                // 输出图片
                System.IO.MemoryStream ms = new System.IO.MemoryStream();
                bmp.Save(ms, System.Drawing.Imaging.ImageFormat.Png);
                this.Response.ContentType = "image/png";
                ms.WriteTo(this.Response.OutputStream);
                ms.Close();
            }//using
            myFont.Dispose();
        }
    }
}