ASP.net实现验证码技术

 

第一步生成验证码

新增一个ValidateCode.aspx页面

在ValidateCode.aspx.cs的代码如下

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Drawing;
using System.Drawing.Imaging;

public partial class ValidateCode : System.Web.UI.Page
{   //该页面将用于生成验证码显示
    protected void Page_Load(object sender, EventArgs e)
    {     //调用函数将验证码生成图片
        this.CreateCheckCodeImage(GenerateCheckCode()); 
       
    }
    private string GenerateCheckCode()
    {  //产生五位的随机字符串
        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();
        }

        //Response.Cookies.Add(new HttpCookie("CheckCode", checkCode));
       Session["CheckCode"] = checkCode;//用于客户端校验码比较

        return checkCode;
    }

    private void CreateCheckCodeImage(string checkCode)
    {  //将验证码生成图片显示
        if (checkCode == null || checkCode.Trim() == String.Empty)
            return;

        System.Drawing.Bitmap image = new System.Drawing.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 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, 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);

            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();
        }
    }
}


第二步测试验证码

建立Test.aspx

<form id="form1" runat="server">
    <div>
        
        <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
        <asp:Button ID="Button1" runat="server" Text="Button" OnClick="Button1_Click" /><br />
        &nbsp;
        <asp:Image ID="Image1" runat="server" ImageUrl="~/ValidateCode.aspx" />//该图片将用于显示验证码
        </div>
    </form>

Test.aspx.cs代码

protected void Page_Load(object sender, EventArgs e)
    {
        
    }
    protected void Button1_Click(object sender, EventArgs e)
    {
        
      if (this.TextBox1.Text.ToString().Trim() == Session["CheckCode"].ToString()) { Response.Write("<script lauguage='javascript'>alert('验证成功');</script>"); }
        }