using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Text;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

using System.Web.SessionState;

namespace Identify
{
    [DefaultProperty("Text")]
    [ToolboxData("<{0}:LandpyIdentityControl runat=server></{0}:LandpyIdentityControl>")]
    public class LandpyIdentityControl : WebControl
    {
        [Bindable(true)]
        [Category("Appearance")]
        [DefaultValue("")]
        [Localizable(true)]
        public string Text
        {
            get
            {
                String s = (String)ViewState["Text"];
                return ((s == null) ? String.Empty : s);
            }

set
            {
                ViewState["Text"] = value;
            }
        }

internal static int _wordLength;

[Description("验证码长度")]
        public int WordLength
        {
            get { return LandpyIdentityControl._wordLength; }
            set
            {
                LandpyIdentityControl._wordLength = value;

}
        }

internal static string _value;

[Description("验证码内容")]
        public string Value
        {
            get { return LandpyIdentityControl._value; }
        }

protected override void RenderContents(HtmlTextWriter output)
        {
            //output.Write(Text);           
        }

public LandpyIdentityControl()
            : base(HtmlTextWriterTag.Img)//重写父类的构造（输出流的HTML标记设置为图像类型）
        { }

protected override void AddAttributesToRender(HtmlTextWriter writer)
        {
            base.AddAttributesToRender(writer);
            writer.AddStyleAttribute(HtmlTextWriterStyle.Cursor, "pointer");
            writer.AddAttribute("onclick", "this.src='img.yy?id='+Math.random()");
            writer.AddAttribute(HtmlTextWriterAttribute.Src, "img.yy");
            writer.AddAttribute("alt", "点击刷新");
        }
    }
}

using System;
using System.Collections.Generic;
using System.Text;
using System.Web;
using System.Web.UI.WebControls;
using System.Web.UI;
using System.Web.SessionState;
using System.Drawing;
using System.IO;

namespace Identify
{
    public class LandpyHttpHander : IHttpHandler, IRequiresSessionState
    {
        /// <summary>
        /// 返回验证码字符
        /// </summary>
        /// <param name="codeCount">验证码长度</param>
        /// <returns></returns>
        private string GetRandomNumberString(int codeCount)
        {
            string strChoice = "2,3,4,5,6,7,8,9,A,B,C,D,E,F,G,H,J,K,L,M,N,P,Q,R,S,T,U,V,W,X,Y,Z";
            string[] strResult = strChoice.Split(new Char[] { ',' });
            string strReturn = "";
            Random rnd = new Random();
            for (int i = 0; i < codeCount; i++)
            {
                int j = rnd.Next(strResult.Length);
                strReturn = strReturn + strResult[j].ToString();
            }
            return strReturn;
        }

private Color GetColor()
        {
            return Color.Black;
        }

private Bitmap CreateImage(string str_AuthCode)
        {
            int width = str_AuthCode.Length * 21;
            int height = 30;
            Random rad = new Random();
            Bitmap bmp = new Bitmap(width, height);
            Graphics grp = Graphics.FromImage(bmp);// 在图片上绘制图形
            grp.Clear(Color.LightGreen);
            grp.DrawRectangle(new Pen(Color.DarkGreen, 1), 0, 0, width - 1, height - 1);
            //画图片的背景噪音线
            for (int i = 0; i < 15; i++)
            {
                int x1 = rad.Next(width);
                int x2 = rad.Next(width);
                int y1 = rad.Next(height);
                int y2 = rad.Next(height);

grp.DrawLine(new Pen(Color.Black), x1, y1, x2, y2);
            }
            //画图片的前景噪音点
            for (int i = 0; i < 100; i++)
            {
                int x = rad.Next(width);
                int y = rad.Next(height);

bmp.SetPixel(x, y, Color.Black);
            }
            Font f = new Font("宋体", 20, FontStyle.Bold);
            Brush br = new SolidBrush(Color.Black);
            for (int i = 0; i < str_AuthCode.Length; i++)
            {
                string s = str_AuthCode.Substring(i, 1);
                Point p = new Point(i * 20 + rad.Next(3), rad.Next(3) + 1);
                grp.DrawString(s, f, br, p);
            }
            grp.Dispose();
            return bmp;

}

/// <summary>
        /// 是否可以处理远程的HTTP请求
        /// </summary>
        public bool IsReusable
        {
            get { return true; }
        }

/// <summary>
        /// 将验证码图片发送给WEB浏览器
        /// </summary>
        /// <param name="context"></param>
        public void ProcessRequest(HttpContext context)
        {
            int size = LandpyIdentityControl._wordLength; //Int32.Parse((String)context.Session["Size"]);
            MemoryStream ms = new MemoryStream();
            string NumStr = GetRandomNumberString(size);
            LandpyIdentityControl._value = NumStr;
            //context.Session.Add("value", NumStr);//将验证码字符保存到session里面
            Bitmap theBitmap = CreateImage(NumStr);
            theBitmap.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
            context.Response.ClearContent();
            context.Response.ContentType = "image/jpeg"; //需要输出图象信息 要修改HTTP头为jpeg类型 
            context.Response.BinaryWrite(ms.ToArray()); 
            theBitmap.Dispose();
            ms.Close();
            ms.Dispose();
            context.Response.End();
        }

}
}