asp.net生成图片验证码

生成图片部分是《ASP.NET从入门到精通》书上的例子------------------------------------

首先，Login页面

 <img src="CreateImage.aspx" onclick="this.src='CreateImage.aspx'" alt="点击刷新" style="cursor:pointer" />

其次，生成图片：CreateImage.aspx代码如下

    public partial class CreateImage : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                string validateString = CreateRandomNumber(4);
                Createimage(validateString);
                Session["ValidateString"] = validateString;
            }

        }
        private string CreateRandomNumber(int numberCount)
        {
            string allChar = "1,2,3,4,5,6,7,8,9,a,b,c,d,e,f,g,h,i,g,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z";

            string[] allCharArr = allChar.Split(',');
            string randomNumber = "";
            Random rand = new Random();
            int temp = -1;
            for (int i = 0; i < numberCount; i++)
            {
                if (temp != -1)
                {
                    rand = new Random(i*temp*(int)(DateTime.Now.Ticks));
                }

                int t = rand.Next(35);
                if (t == temp)
                {
                    return CreateRandomNumber(numberCount);
                }
                temp = t;
                randomNumber += allCharArr[t];
            }
            return randomNumber;
        }
        private void Createimage(string validateString)
        {
            if (validateString == null || validateString.Trim() == string.Empty)
            {
                return;
            }
            //create a bitmap image
            Bitmap image = new Bitmap(validateString.Length * 12 + 10, 22);
            Graphics g = Graphics.FromImage(image);
            try
            {
                //随机生成器
                Random rand = new Random();
                g.Clear(Color.White);
                for (int i = 0; i < 25; i++)
                {
                    int x1 = rand.Next(image.Width);
                    int x2 = rand.Next(image.Width);
                    int x3 = rand.Next(image.Height);
                    int x4 = rand.Next(image.Height);
                    g.DrawLine(new Pen(Color.Silver), x1, x2, x3, x4);

                }
                Font font = new Font("Arial", 12, FontStyle.Bold);
                LinearGradientBrush brush = new LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.DarkRed, 1.2f, true);

                g.DrawString(validateString, font, brush, 2, 2);
                //绘制图片的前景噪声点
                for (int i = 0; i < 100; i++)
                {
                    int x = rand.Next(image.Width);
                    int y = rand.Next(image.Height);
                    image.SetPixel(x, y, Color.FromArgb(rand.Next()));
                }
                //绘制图片的边框   
                g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);
                MemoryStream ms = new MemoryStream();
                //将图像保存在指定的流
                image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
                Response.ClearContent();
               
                //Response.CacheControl = "no-cache";
                Response.ContentType = "image/Gif";
                Response.BinaryWrite(ms.ToArray());
            }
            finally
            {
                g.Dispose();
                image.Dispose();

            }

        }
    }

还是挺好看的，备用。。。。。。。