Login 图片验证码， 用一个aspx页面作为图片验证码

第二种是：比较简单，生成的不是图片，是span和文字版的验证码

1、类库文件

<ccid_nobr>

<ccid_code>using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Web.UI;
using System.ComponentModel;
using System.Web.UI.WebControls;
using System.Drawing;
using System.Web;
using System.IO;

namespace MyControls
{
    [ParseChildren(false)]
    [DefaultProperty("Text")]
    [ToolboxData("<{0}:ValidateControl runat=server></{0}:ValidateControl>")]
    public class ValidateControl : WebControl
    {
        public ValidateControl() : base(HtmlTextWriterTag.Img)
        { }
        

        #region 属性

        [Category("Appearance"),
 PersistenceMode(PersistenceMode.InnerDefaultProperty),
 Bindable(true), DefaultValue("GBK5"), 
Localizable(true), Description("Label_Text")]
        public virtual string Text
        {
            get
            {
                String s = (String)ViewState["Text"];
                return ((s == null) ? "GK4W" : s);
            }
            set
            {
                ViewState["Text"] = value;
            }
        }

        [BrowsableAttribute(true)]
        [DescriptionAttribute("背景图片")]
        [CategoryAttribute("Appearance")]
        public virtual String ImageUrl
        {
            get { return ViewState["ImageUrl"] != null ? (string)ViewState["ImageUrl"] : ""; }
            set { ViewState["ImageUrl"] = value; }
        }

        [BrowsableAttribute(true)]
        [DescriptionAttribute("数据位数")]
        [CategoryAttribute("Appearance")]
        public virtual int Step
        {
            get { return ViewState["Step"] != null ? (int)ViewState["Step"] : 4; }
            set { ViewState["Step"] = value; }
        }

        [BrowsableAttribute(true)]
        [DescriptionAttribute("文本位置")]
        [CategoryAttribute("Appearance")]
        public virtual TextAlign TextAlign
        {
            get { return ViewState["TextAlign"] != null ? 
(TextAlign)ViewState["TextAlign"] : 
DX.GO.Portal.Web.Controls.TextAlign.center; }
            set { ViewState["TextAlign"] = value; }
        }

        protected override HtmlTextWriterTag TagKey
        {
            get
            {
                return HtmlTextWriterTag.Span;
            }
        }
        #endregion

        #region 初始化

        protected override void OnLoad(EventArgs e)
        {
            Text = GenerateCheckCode(Step);
            //CreateCheckCodeImage(Text);
            base.OnLoad(e);
        }
        #endregion

        #region 内部方法

        /// <summary>
        /// 产生随机字符串
        /// </summary>
        /// <param name="num">int</param>
        /// <returns>string</returns>
        private string GenerateCheckCode(int num)
        {
            #region 
            //string[] source ={"0","1","2","3","4","5","6","7","8","9",
            //                    "A","B","C","D","E","F","G","H","I","J","K","L","M","N",
            //                    "O","P","Q","R","S","T","U","V","W","X","Y","Z"};
            //string code = "";
            //Random rd = new Random();
            //for (int i = 0; i < num; i++)
            //{
            //    code += source[rd.Next(0, source.Length)];
            //}
            //return code;
            #endregion

            int number;
            char code;
            string checkCode = String.Empty;

            Random random = new Random();
            for (int i = 0; i < num; i++)
            {
                number = random.Next();

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

                checkCode += code.ToString();
            }
            return checkCode;
        }

        /// <summary>
        /// 生成图片
        /// </summary>
        /// <param name="checkCode">string</param>
        private void CreateCheckCodeImage(string checkCode)
        {
            if (checkCode == null || checkCode.Trim() == String.Empty)
                return;

            //Bitmap image = new Bitmap((int)Math.Ceiling((checkCode.Length * 12.5)), 22);
          
            Bitmap image = new Bitmap((int)this.Width.Value,(int)this.Height.Value);
            Graphics g = Graphics.FromImage(image);

            try
            {
                //生成随机生成器
                Random random = new Random();

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

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

                    g.DrawLine(new Pen(Color.GreenYellow), x1, y1, x2, y2);
                }

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

                //画图片的前景噪音点
                for (int i = 0; i < 80; i++)
                {
                    int x = random.Next(image.Width);
                    int y = random.Next(image.Height);

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

                //画图片的边框线
                g.DrawRectangle(new Pen(Color.Red), 0, 0, image.Width - 1, image.Height - 1);

                System.IO.MemoryStream ms = new System.IO.MemoryStream();
                image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);

                System.Web.HttpContext.Current.Response.ClearContent();
                System.Web.HttpContext.Current.Response.ContentType = "image/Gif";
                System.Web.HttpContext.Current.Response.BinaryWrite(ms.ToArray());
                System.Web.HttpContext.Current.Response.End();
            }
            finally
            {
                g.Dispose();
                image.Dispose();
            }
        }


        #endregion

        #region 呈现

        /// <summary>
        /// 应用最外层标签的属性和样式属性
        /// </summary>
        /// <param name="writer"></param>
        protected override void AddAttributesToRender(System.Web.UI.HtmlTextWriter writer)
        {
            writer.AddAttribute(HtmlTextWriterAttribute.Name, this.UniqueID);
            writer.AddStyleAttribute(HtmlTextWriterStyle.Height, Convert.ToString(Height));
            writer.AddStyleAttribute(HtmlTextWriterStyle.Width, Convert.ToString(Width));
            writer.AddStyleAttribute(HtmlTextWriterStyle.BackgroundImage, ImageUrl);
            writer.AddStyleAttribute(HtmlTextWriterStyle.TextAlign, Convert.ToString(TextAlign));
            base.AddAttributesToRender(writer);
        }

        /// <summary>
        /// 过滤
        /// </summary>
        /// <param name="obj"></param>
        protected override void AddParsedSubObject(object obj)
        {
            //if (!(obj is LiteralControl))
            //    return;
            //base.AddParsedSubObject(obj);
        }

        /// <summary>
        /// 呈现最外层标签的内容
        /// </summary>
        /// <param name="output"></param>
        protected override void RenderContents(HtmlTextWriter output)
        {
            output.Write(Text);
            base.RenderContents(output);
        }

        #endregion
    }
}


using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace MyControls
{
    public enum TextAlign
    {
        right, center, left
    }
}

2、生成文件，添加到工具箱，拖到页面就可以使用

<ccid_nobr>

<ccid_code><go:ValidateControl ID="ValidateControl1" 
runat="server" BackColor="#CC3300" 
                                                
BorderStyle="Solid" BorderWidth=
"1px" Font-Bold="True" Font-Italic="True" 
                                                
Font-Names="Arial Black" Font-Size="Small" Step="5" Width="70px">
</go:ValidateControl>

3、验证方法

<ccid_nobr>

<ccid_code>string vcode = string.Empty;        
       protected void Page_Load(object sender, EventArgs e)
        {
            vcode = ((ValidateControl)this.Login.FindControl("ValidateControl1")).Text.ToLower();
        }
   
       protected void Login_Authenticate(object sender, AuthenticateEventArgs args)
        {
            string Codetext = ((TextBox)this.Login.FindControl("txtValidateCode")).Text.ToLower();
           if (Codetext == null)
            {
                this.Login.FailureText = "验证码不能为空！";
                args.Authenticated = false;
                return;
            }

           if (vcode == Codetext)
           {
               AuthLogCount(mycount.LogCounts, args);
           }
           else
           {
               this.Login.FailureText = "验证码输入不正确！";
               args.Authenticated = false;
               return;
           }
        }