验证码控件

    
        自定义控件部分    
                

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.Drawing;
using System.IO;
using System.Drawing.Imaging;
namespace CheckImageLib
{
    [DefaultProperty("Text")]
    [ToolboxData("<{0}:CheckImages runat=server></{0}:CheckImages>")]
    public class CheckImages : 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;
            }
        }

     
        protected override void Render(HtmlTextWriter output)
        {

            output.Write(this.CreateCheckCodeImage(GenerateCheckCode()));

            //output.Write("");
        }
        private string GenerateCheckCode()
        {
            int number;
            char code;
            string checkCode = String.Empty;

            System.Random random = new Random();

            for (int i = 0; i < 5; i++)
            {
                number = random.Next();

                if (number % 2 == 0)
                    code = (char)('0' + (char)(number % 10));
                else
                    code = (char)('A' + (char)(number % 26));

                checkCode += code.ToString();
            }
         
          
            HttpContext.Current.Response.Cookies.Add(new HttpCookie("CheckCode", checkCode));

            return checkCode;
        }

        private string CreateCheckCodeImage(string checkCode)
        {
            if (checkCode == null || checkCode.Trim() == String.Empty)
                return "";

            System.Drawing.Bitmap bm = new System.Drawing.Bitmap((int)Math.Ceiling((checkCode.Length * 12.5)), 22);
            Graphics bp = Graphics.FromImage(bm);
            
                //生成随机生成器
                Random random = new Random();

                //清空图片背景色
                bp.Clear(Color.White);

                //画图片的背景噪音线
                for (int i = 0; i < 25; i++)
                {
                    int x1 = random.Next(bm.Width);
                    int x2 = random.Next(bm.Width);
                    int y1 = random.Next(bm.Height);
                    int y2 = random.Next(bm.Height);

                    bp.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);
                }

                Font font = new System.Drawing.Font("Arial", 12, (System.Drawing.FontStyle.Bold | System.Drawing.FontStyle.Italic));
                System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(0, 0, bm.Width, bm.Height), Color.Blue, Color.DarkRed, 1.2f, true);
                bp.DrawString(checkCode, font, brush, 2, 2);

                //画图片的前景噪音点
                for (int i = 0; i < 100; i++)
                {
                    int x = random.Next(bm.Width);
                    int y = random.Next(bm.Height);

                   bm.SetPixel(x, y, Color.FromArgb(random.Next()));
                }

                //画图片的边框线
                bp.DrawRectangle(new Pen(Color.Silver), 0, 0, bm.Width - 1, bm.Height - 1);

             
               


                  FileStream fs = new FileStream(Page.Server.MapPath(Page.Request.Url.AbsolutePath.Replace(".aspx", ".jpg")), FileMode.Create);
                  bm.Save(fs, ImageFormat.Jpeg);

                  bm.Dispose();
                  bp.Dispose();
                  fs.Close();

                  return "<img src=" + Page.Request.Url.AbsolutePath.Replace(".aspx", ".jpg") + " ></img>";

                
            }
           



      

    }
}

调用部分

 <form id="form1" runat="server">
    <div>
        &nbsp;<asp:TextBox ID="txtCheckCode" runat="server"></asp:TextBox>
        <asp:Label ID="lblMessage" runat="server"></asp:Label></div>
        <asp:Button ID="Button1" runat="server" OnClick="Button1_Click" Text="Button" />&nbsp;
       
        
        <table>
        <tr>
        <td style=" 7px">  
   
            &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;<cc1:CheckImages ID="CheckImages1" runat="server" />
            &nbsp;
            &nbsp; &nbsp;
            &nbsp;
            &nbsp;&nbsp;</td>
        </tr>
        </table>
    </form>

  protected void Button1_Click(object sender, EventArgs e)
        {
            if (Request.Cookies["CheckCode"] == null)
            {
                lblMessage.Text = "您的浏览器设置已被禁用 Cookies，您必须设置浏览器允许使用 Cookies 选项后才能使用本系统。";
                lblMessage.Visible = true;
                return;
            }

            if (String.Compare(Request.Cookies["CheckCode"].Value, txtCheckCode.Text, true) != 0)
            {
                lblMessage.Text = "验证码错误，请输入正确的验证码。";
                lblMessage.Visible = true;
                return;
            }

        }