.NET中生成随机验证码

在.NET中可以用如下方法生成随机验证码
新建一个窗体,命名为RandomImage.aspx,其后台代码如下:(将文件保存后,在用户注册界面放一个img, 将其imgUrl属性改为RandomImage.aspx就可以了

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.Drawing2D;
using System.IO;
using System.Drawing.Imaging;

public partial class RandomImage : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        CreateCheckCodeImage(GenerateCheckCode());
    }

    private string GenerateCheckCode()
    {
        int number;
        string strCode = string.Empty;

        //随机数种子

        Random random = new Random();

        for (int i = 0; i < 4; i++)//校验码长度为4
        {
            //随机数的整数
            number = random.Next();

            //字符从0-9,A-Z中随机产生对应的ASCII码分别为
            //48-57,65-90
            number = number % 36;
            if (number < 10)
            {
                number += 48;
            }
            else
            {
                number += 55;
            }

            strCode += ((char)number).ToString();
        }
        //在Cookie中保存校验码
        Response.Cookies.Add(new HttpCookie("CheckCode", strCode));
        return strCode;
    }
    ///<summary>
    ///根据校验码输出图片
    ///</summary>
    ///<param name="checkCode">产生的随机校验码</param>

    private void CreateCheckCodeImage(string checkCode)
    {
        //若校验码为空,则直接返回
        if (checkCode == null || checkCode.Trim() == String.Empty)
            return;
        //根据校验码的长度确定输出图片的长度
        System.Drawing.Bitmap image = new System.Drawing.Bitmap((int)Math.Ceiling(Convert.ToDecimal(checkCode.Length * 15)), 20);
        //创建Graphics对象
        Graphics g = Graphics.FromImage(image);

        try
        {
            //生成随机数种子
            Random random=new Random();

            //清空图片背景色
            g.Clear(Color.White);

            //画图片的背景噪音线10条

            for(int i=0;i<10;i++)
            {
                //噪音线起点坐标(x1,y1),终点坐标(x2,y2)

                int x1=random.Next(image.Width);
                int x2=random.Next(image.Width);
                int y1=random.Next(image.Height);
                int y2=random.Next(image.Height);

                //用银色线画出噪音线
                g.DrawLine(new Pen(Color.Silver),x1,y1,x2,y2);
            }

            //输出图片中校验码的字体:12号Arial,粗斜体

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

            //线性渐变画刷
            LinearGradientBrush brush=new LinearGradientBrush(new Rectangle(0,0,image.Width,image.Height),Color.Blue,Color.Purple,1.2f,true);
            g.DrawString(checkCode,font,brush,2,2);

            //画图片的前景噪音点50个
            for(int i=0;i<50;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.SaddleBrown),0,0,image.Width-1,image.Height-1);

            //创建内存流用于输出图片
            using(MemoryStream ms=new MemoryStream())
            {
                //图片格式指定为png
                image.Save(ms,ImageFormat.Png);

                //清除缓冲区流中的所有输出
                Response.ClearContent();

                //输出流的HHT MIME类型设置为"image/png"
                Response.ContentType="image/Png";

                //输出的图片的二进制流
                Response.BinaryWrite(ms.ToArray());
            }
        }
        finally
        {
            //释放Bitmap对象和Graphics对象
            g.Dispose();
            image.Dispose();
        }
       
       
        }

   
    }

 

有什么地方不懂的话,加我QQ:89141312