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完整asp.net圖形驗證碼程式

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1、測試頁面：Default.aspx

<%@ Page Language="C#" AutoEventWireup="true"  CodeFile="Default.aspx.cs" Inherits="_Default" %>
 
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
 
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>ASP.NET驗證碼</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        請輸入驗證碼：<input id="txtVI" type="text" name="view_id" runat="server" maxlength="5" size="5"/>
     <asp:Image id="Image1" runat="server" ImageUrl="ValidateCode.aspx" ImageAlign="Middle" />
        <asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server" ErrorMessage="您沒有輸入驗證碼" ControlToValidate="txtVI"></asp:RequiredFieldValidator><br />
        <asp:Button ID="Button1" runat="server" Text="提　交" OnClick="Button1_Click" /></div>
    </form>
</body>
</html>

2、測試頁面後台：Default.aspx.cs

using System;
using System.Data;
using System.Configuration;
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;
 
public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
 
    }
    protected void Button1_Click(object sender, EventArgs e)
    {
        string VNum;
        VNum = Session["VNum"].ToString();
        Session.Abandon();
        ViewState["VNum"] = VNum;
        if (txtVI.Value == ViewState["VNum"].ToString())
        {
            Response.Write("<script>alert('驗證碼輸入正確！');</script>");
            return;
        }
        else
        {
            // VIWShow.Text="所填寫的驗證碼不正確！";
            Response.Write("<script>alert('驗證碼輸入錯誤！');</script>");
            return;
        }
    }
}

3、產生驗證碼頁面:ValidateCode.aspx

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="ValidateCode.aspx.cs" Inherits="ValidateCode" %>

4、產生驗證碼頁面後台：

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;
 
/* Copyright all(c) 2005 ZhongFeng, http://blog.csdn.net/SW515 */
public partial class ValidateCode : System.Web.UI.Page
{
    private void Page_Load(object sender, System.EventArgs e)
    {
        this.CreateCheckCodeImage(GenerateCheckCode());
    }
 
    #region Web Form設計器產生的程式碼
    override protected void OnInit(EventArgs e)
    {
        //
        // CODEGEN: 該調用是 ASP.NET Web Form設計器所必需的。
        //
        InitializeComponent();
        base.OnInit(e);
    }
 
    /// <summary>
    /// 設計器支援所需的方法 - 不要使用代碼編輯器修改
    /// 此方法的內容。
    /// </summary>
    private void InitializeComponent()
    {
        this.Load += new System.EventHandler(this.Page_Load);
    }
    #endregion
 
    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();
        }
 
        Session["VNum"] = 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 * 12.5)), 22);
        System.Drawing.Graphics g = Graphics.FromImage(image);
 
        try
        {
            //產生隨機產生器
            Random random = new Random();
 
            //清空圖片背景色
            g.Clear(Color.White);
 
            //畫圖片的背景雜音線
            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);
 
            //畫圖片的前景噪音點
            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()));
            }
 
            //畫圖片的邊框線
            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();
        }
    }
}

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