c#生成随机彩色验证码例子

一个简单的例子实现根据验证码判断登陆。

登陆页：

 <table>
            <tr>
                <td style="text-align: right; height: 40px; width: 100px;">
                    <asp:TextBox ID="txtCheckCode" runat="server" Height="25px" Width="97px" ValidationGroup="1"></asp:TextBox>
                </td>
                <td style="text-align: center; height: 40px; width: 100px;">
                    <img id="chkCode" src="CheckCode.aspx" onclick="javascript:CheckCode();" style="cursor: pointer" />
                </td>
                <td>
                    &nbsp;
                    <asp:RequiredFieldValidator ID="RequiredFieldValidator2" runat="server" ControlToValidate="txtCheckCode"
                        ErrorMessage="请输入验证码！" ForeColor="Red" ValidationGroup="1"></asp:RequiredFieldValidator>
                </td>
                <td>
                <asp:Button  ID="btn" Text="登陆" runat="server" onclick="btn_Click" ValidationGroup="1" Style="height: 20px" />
                <asp:Label ID="zt" ForeColor="Red" runat="server"></asp:Label>
                </td>
            </tr>
        </table>

登陆页js： 这里主要实现点击验证码在重新生成验证码。

 <script language="javascript" type="text/javascript" src="./Scripts/jquery-1.4.1.min.js"></script>
     <script language="javascript" type="text/javascript">
         function CheckCode() {
             $("#chkCode").attr("src", "./CheckCode.aspx?" + Math.random());
         }
</script>

登陆页面后台.CS

 protected void btn_Click(object sender, EventArgs e)
        {
            string checkCode =txtCheckCode.Text.Trim();
            string ischeck = Session["UserCCode"].ToString();
            if (!string.IsNullOrEmpty(checkCode)
                  && ischeck.Equals(checkCode))
            {
                this.zt.Text = "登陆成功！";
            }
            else
            {
                this.zt.Text = "登陆失败！";
            }
        }

CheckCode.aspx 验证码检查页面：

using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Drawing;

public partial class CheckCode : System.Web.UI.Page
{
    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();
        }
        //Response.Cookies.Add(new HttpCookie("CheckCode", checkCode));
        Session["UserCCode"] = checkCode;
        return checkCode;
    }

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

        System.Drawing.Bitmap image = new System.Drawing.Bitmap((int)Math.Ceiling((checkCode.Length * 14.5)), 26);
        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 System.Drawing.Font("Arial", 13, (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.DarkTurquoise, 1.2f, true);
            g.DrawString(checkCode, font, brush, 6, 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);

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

实现效果：

源码下载：http://download.csdn.net/detail/njxiaogui/5279096