.NET验证码控件（美观 易用）

<%@ WebHandler Language="C#" Class="verify" %>

using System;
using System.Web;

using System.Text;
using System.IO;
using System.Drawing;
using System.Drawing.Imaging;

public class verify : IHttpHandler, System.Web.SessionState.IRequiresSessionState
{

    public void ProcessRequest(HttpContext context)
    {
        Code gif = new Code();//初始化验证码生成类  
        string valid = "";//定义随机数  
        MemoryStream ms = gif.Create(out valid);//获取包括验证码图片的内存流  
        context.Session["gif"] = valid;//验证码存储在Session中，供验证。  
        context.Response.ClearContent();//清空输出流  
        context.Response.ContentType = "image/png";//输出流的格式  
        context.Response.BinaryWrite(ms.ToArray());//输出  
        context.Response.End();
    }
    public bool IsReusable
    {
        get
        {
            return false;
        }
    }  

}


public class Code
{
    /// <summary>  
    /// 该方法用于生成指定位数的随机数  
    /// </summary>  
    /// <param name="VcodeNum">参数是随机数的位数</param>  
    /// <returns>返回一个随机数字符串</returns>  
    private string RndNum(int VcodeNum)
    {
        //验证码可以显示的字符集合  
        //string Vchar = "1,1,2,3,4,5,6,7,8,9,a,b,c,d,e,f,g,h,i,j,k,l,m,n,p,p" +
        //    ",q,r,s,t,u,v,w,x,y,z,A,B,C,D,E,F,G,H,I,J,K,L,M,N,P,P,Q" +
        //    ",R,S,T,U,V,W,X,Y,Z";
        string Vchar = "1,2,3,4,5,6,7,8,9";//=================================================这里使用纯数字
        string[] VcArray = Vchar.Split(new Char[] { ‘,‘ });//拆分成数组  
        string VNum = "";//产生的随机数  
        int temp = -1;//记录上次随机数值，尽量避避免生产几个一样的随机数  

        Random rand = new Random();
        //采用一个简单的算法以保证生成随机数的不同  
        for (int i = 1; i < VcodeNum + 1; i++)
        {
            if (temp != -1)
            {
                rand = new Random(i * temp * unchecked((int)DateTime.Now.Ticks));//初始化随机类  
            }
            //int t = rand.Next(61);//获取随机数  
            int t = rand.Next(9);//======================================================与VcArray定义的长度匹配
            if (temp != -1 && temp == t)
            {
                return RndNum(VcodeNum);//如果获取的随机数重复，则递归调用  
            }
            temp = t;//把本次产生的随机数记录起来  
            VNum += VcArray[t];//随机数的位数加一  
        }
        return VNum;
    }

    /// <summary>  
    /// 该方法是将生成的随机数写入图像文件  
    /// </summary>  
    /// <param name="VNum">VNum是一个随机数</param>  
    public MemoryStream Create(out string VNum)
    {
        VNum = RndNum(4);
        Bitmap Img = null;
        Graphics g = null;
        MemoryStream ms = null;
        System.Random random = new Random();
        //验证码颜色集合  
        Color[] c = { Color.Black, Color.Red, Color.DarkBlue, Color.Green, Color.Orange, Color.Brown, Color.DarkCyan, Color.Purple };
        //验证码字体集合  
        string[] fonts ={ "Verdana", "Microsoft Sans Serif", "Comic Sans MS", "Arial", "宋体" };


        //定义图像的大小，生成图像的实例  
        Img = new Bitmap((int)VNum.Length * 18, 32);

        g = Graphics.FromImage(Img);//从Img对象生成新的Graphics对象    

        g.Clear(Color.White);//背景设为白色  

        //在随机位置画背景点  
        for (int i = 0; i < 100; i++)
        {
            int x = random.Next(Img.Width);
            int y = random.Next(Img.Height);
            g.DrawRectangle(new Pen(Color.LightGray, 0), x, y, 1, 1);
        }
        //验证码绘制在g中  
        for (int i = 0; i < VNum.Length; i++)
        {
            int cindex = random.Next(7);//随机颜色索引值  
            int findex = random.Next(5);//随机字体索引值  
            Font f = new System.Drawing.Font(fonts[findex], 20, System.Drawing.FontStyle.Bold);//字体======================字体大小  
            Brush b = new System.Drawing.SolidBrush(c[cindex]);//颜色  
            int ii = 4;
            if ((i + 1) % 2 == 0)//控制验证码不在同一高度  
            {
                ii = 2;
            }
            g.DrawString(VNum.Substring(i, 1), f, b, 3 + (i * 12), ii);//绘制一个验证字符  
        }
        ms = new MemoryStream();//生成内存流对象  
        Img.Save(ms, ImageFormat.Jpeg);//将此图像以Png图像文件的格式保存到流中  

        //回收资源  
        g.Dispose();
        Img.Dispose();
        return ms;
    }

} 

<asp:TextBox ID="txtVerify" runat="server" MaxLength="4" Width="100px" CssClass="txtin2" Height="18px"></asp:TextBox>
<img src=‘verify.ashx‘ style="width:100px;height:30px" id="verify"/>
<a href=‘javascript:verify();‘>看不清，换一张</a>

function verify(){
    $("#verify").attr("src","verify.ashx");
}

if (txtVerify.Text == "")
        {
            this.ClientScript.RegisterStartupScript(this.GetType(), "scriptKey", "alert(‘验证码不能为空！‘)", true);
        }
        else if (String.Compare(Session["gif"].ToString(), txtVerify.Text, true) != 0)
        {
            txtVerify.Text = "";
            this.ClientScript.RegisterStartupScript(this.GetType(), "scriptKey", "alert(‘验证码有误,请重新输入正确的验证码！‘)", true);
        }
        else
        {
            //通过验证
}