随机产生
public class picture : System.Web.UI.Page
    {
        char[] arrc={'0','1','2','3','4','5','6','7','8','9','a','A','b','B','c','C','d','D'};
        private void Page_Load(object sender, System.EventArgs e)
        {
            // 在此处放置用户代码以初始化页面            
            Response.Clear();
            Response.ContentType="image/jpeg";
            string str1=this.genrandom(6);
            Session["rdcode"]=str1;
            this.genpicture(str1);
        }
        private string genrandom(int i)
        {
            Random rm=new Random();
            string str1=null;
            for(int j=1;j<=i;j++)
            {
                str1+=arrc[rm.Next(arrc.Length)];
            }
            return str1;
        }
        private void genpicture(string str1)
        {
            Bitmap bm=new Bitmap(90,24);            
            Graphics gp=Graphics.FromImage(bm);
            //gp.Clear(Color.Blue);
            //Pen p1=new Pen(Color.Yellow,2);
            //gp.DrawRectangle(p1,10,2,180,20);
            gp.DrawString(str1,new Font("宋体",14,FontStyle.Bold),new SolidBrush(Color.Yellow),new Rectangle(10,2,70,20));
            gp.Save();
            bm.Save(Response.OutputStream,ImageFormat.Jpeg);
            //bm.Save("c:/a.jpg",ImageFormat.Jpeg);

        }

谢谢这为大侠!不过好象要要一写图片放到文件夹了,是不?就是那些数字?
可有些代码我还是看不懂

这个是利用asp.net的作图功能，不用建立文件夹就行了，
直接就会出现图片了

可以告诉我界面里都需要添加那些控件呢?