用户登录验证随机数图片的产生

首先在HTML页面中添加<span id="spRandomNum" runat="server"></span>
然后在后台Load事件中添加如下代码

1 Random rndm = new Random();
2 string strNum = rndm.Next(1, 9999).ToString("0000");
3
4 System.Drawing.Image img = new System.Drawing.Bitmap(100, 25);
5
6 System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(img);
7 System.Drawing.Font fnt = new System.Drawing.Font("Arial", 12, System.Drawing.FontStyle.Regular);
8 System.Drawing.Brush brsh = System.Drawing.Brushes.Black;
9 System.Drawing.Pen pn = new System.Drawing.Pen(System.Drawing.Color.Black, 0);
10 g.Clear(System.Drawing.Color.FromArgb(255, 255, 255));
11 g.DrawString(strNum, fnt, brsh, 2, 2);
12
13 //这个地方要保证是绝对路径的，我此处的images是我项目中的文件夹
14 if (System.IO.File.Exists(@"E:\Carl\webTest\WebSite2\images\random.Gif"))
15 System.IO.File.Delete(@"E:\Carl\webTest\WebSite2\images\random.Gif");
16 img.Save(@"E:\Carl\webTest\WebSite2\images\random.Gif", System.Drawing.Imaging.ImageFormat.Gif);
17
18 spRandomNum.InnerHtml = "<img src=\"images/random.Gif\" />";