.NET验证码

转载的验证码，微改后验证码如下：

CheckCode.aspx.cs代码如下：

protected void Page_Load(object sender, EventArgs e)
        {
            this.CreateCheckCodeImage(GenerateCheckCode());
        }

        private string GenerateCheckCode()
        {
            int number;
            char code;
            string checkCode = string.Empty;

            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();//获取编码数
            }
            Session["CheckCode"] = checkCode;
            return checkCode;
        }

        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);
            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.Silver), x1, y1, x2, y2);
                }

                Font font = new Font("Arial", 12, (FontStyle.Bold | FontStyle.Italic | FontStyle.Underline));

                LinearGradientBrush brush = new 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 < 100; 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.Silver), 0, 0, image.Width - 1, image.Height - 1);

                MemoryStream ms = new MemoryStream();
                image.Save(ms, ImageFormat.Gif);
                Response.ClearContent();
                Response.ContentType = "image/Gif";
                Response.BinaryWrite(ms.ToArray());
            }
            finally
            {
                g.Dispose();
                image.Dispose();
            }
        }

 调用CheckCode.aspx文件代码如下：

<td class="tbleft">
     <asp:TextBox ID="txtUserCoder" runat="server"></asp:TextBox>

 <img id="CodeImg" src="WebCode.aspx" onclick="document.getElementById('CodeImg').src='WebCode.aspx?tmp='+Math.random()" style="cursor:pointer;"/>

</td>