ASP.NET实现验证码

首先外观显示页面代码：

 1protected System.Web.UI.WebControls.Image ValidateImage;
 2
 3        private void Page_Load(object sender, System.EventArgs e)
 4        {
 5            if(!IsPostBack)
 6            {
 7                //验证码的生成和获取，用于登录页面的有效验证。
 8                string ValidCode = DB.CheckCode.MakeValidateCode();
 9                ValidateImage.ImageUrl = "xbm.aspx?code="+ ValidCode;
10                ViewState["ValidCode"] = ValidCode;
11                ViewState["CheckCode"]=DB.CheckCode.DecodeValidateCode(ViewState["ValidCode"].ToString());
12                ary_chk=new ArrayList();
13                ary_chk.Add(ViewState["CheckCode"]);
14                ary_chk.Add(System.DateTime.Now);
15                //判断输入的验证码是否正确
16                BtnSub.Attributes["onclick"]="return Check(\""+ViewState["CheckCode"].ToString()+"\");";
17            }
18        }

以下为处理验证码类：

//获取随机生成的验证码类
public class CheckCode
    {
        public static string DecodeValidateCode(string code)
        {
            char [] s = code.ToCharArray();
            return String.Format("{0}{1}{2}{3}", s[0],s[9],s[3],s[7]);
        }
        
        //随机生成验证码序列
        public static string MakeValidateCode()
        {
            char[] s = new char[]{ '2','3','4','5','6','7','8','9','a'
                                     ,'b','c','d','e','f','g','h','i','j','k','m','n','p','q'
                                     ,'r','s','t','u','v','w','x','y','z'};

            string num = "";
            Random r = new Random();
            for(int i = 0; i < 10; i++)
            {
                num += s[r.Next(0, s.Length)].ToString(); 
            }
            return num;
        }
    }

把接收的验证码转为图片xbm.aspx?code=生成的验证玛：

        private void Page_Load(object sender, System.EventArgs e)
        {
            if (!IsPostBack)
            {
                if (Request["code"] != null)
                {
                    string Validcode = Request["code"];
                    //进行验证码长度的判断
                    if (Validcode.Length <10)
                    {
                        Validcode = "3360";
                    }
                    else
                    {
                        //获取验证码
                        Validcode = DB.CheckCode.DecodeValidateCode(Validcode);
                    }
                    ValidateCode code =new ValidateCode();
                    //画出验证码
                    code.DrawValidateCode(this, Validcode);
                }
}

//实现一个验证码的类

        public class ValidateCode
        {
            private Bitmap validateimage;
            private Graphics g;
            public ValidateCode()
            {
                validateimage = new Bitmap(40, 17, PixelFormat.Format24bppRgb);
                g = Graphics.FromImage(validateimage);
            }
            //设置验证码的相关属性
            public void DrawValidateCode(Page e, string i)
            {
                g.FillRectangle(new SolidBrush(Color.FromArgb(0xee,0xee,0xee)), 0, 0, 40, 17);
                g.DrawString(i, new Font("宋体",12),new SolidBrush(Color.Black),new PointF(1,0));
                g.Save();
                MemoryStream ms=new MemoryStream();
                validateimage.Save(ms,System.Drawing.Imaging.ImageFormat.Gif);
                e.Response.ClearContent();
                e.Response.ContentType="image/gif";
                e.Response.BinaryWrite(ms.ToArray());
                e.Response.End();
            }
        }

以上大家可以自己做自己的整和，也可以随自己的意愿进行修改。