ASP.NET 生成驗證碼

直接上code：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Drawing;
using System.Drawing.Imaging;
 
namespace AnalyzerExtAuth.Common
{
    public partial class ValidateCodeImg : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            //驗證碼中可能會出現的字符集合
            String checkCodeString = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
            //驗證碼字符集合的長度
            int length = checkCodeString.Length;
            //設置繪製驗證碼的字體,並設置爲粗體並傾斜
            Font font = new Font("宋體", 24, (FontStyle.Bold | FontStyle.Italic));
            //繪製驗證碼的筆刷
            Brush brush = null;
            //繪製驗證碼文字的顏色
            Color brushColor = new Color();
            //驗證碼的字符串
            String checkCode = String.Empty;
            //當前要繪製的驗證字符
            String code = String.Empty;
            //要生成的驗證碼圖片對象
            Bitmap image = new Bitmap(80, 40);
            //繪圖畫板
            Graphics graphics = Graphics.FromImage(image);
            //填充背景爲白色
            graphics.Clear(Color.White);
 
            //創建隨機數對象
            Random random = new Random();
 
            int x1, x2, y1, y2;
            Pen pen = new Pen(Color.Silver);
            //畫背景噪音線
            for (int i = 1; i <= 25; i++)
            {
                x1 = random.Next(image.Width);
                y1 = random.Next(image.Height);
                x2 = random.Next(image.Width);
                y2 = random.Next(image.Height);
                graphics.DrawLine(pen, x1, y1, x2, y2);
            }
 
            for (int i = 0; i < 4; i++)
            {
                //爲了保證取的字符索引不超過0-35之間
                //取任何數的餘數都肯定小於自身
                //採用當前時間的毫秒 % 驗證碼字符的總長度=當前驗證字符
                int current = random.Next(DateTime.Now.Millisecond) % length;
                //截取驗證字符
                code = checkCodeString.Substring(current, 1);
                //拼接到驗證碼的字符串
                checkCode += code;
                //隨機生成驗證碼字符的顏色
                brushColor = Color.FromArgb(random.Next(256), random.Next(256), random.Next(256));
                //筆刷的顏色
                brush = new SolidBrush(brushColor);
                //繪製剛剛得到的字符串
                graphics.DrawString(code, font, brush, i * 15 + 2, 2);
            }
 
            Response.Clear();
            Response.ContentType = "image/pjpeg";
            //在Session中保存驗證碼字符串,以便與用戶輸入進行比較
            Session["CheckCode"] = checkCode;
            image.Save(Response.OutputStream, ImageFormat.Jpeg);
            image.Dispose();
            Response.End();
 
        }
    }
} 
//驗證控件
< img src = "ValidateCode.aspx" width = "60" height = "25" style = "cursor: pointer;" onclick = "this.src='ValidateCode.aspx?id'+Math.random()*10000" / >

P.S.其中id加上一個隨機數只是爲了網頁能夠刷新重新計算驗證碼。當然我們還可以在後面添加生成驗證碼的長度，以便更好的管理驗證碼複雜性