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
然后在后台Load事件中添加如下代码
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Random rndm = new Random();
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string strNum = rndm.Next(1, 9999).ToString("0000");
3![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
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System.Drawing.Image img = new System.Drawing.Bitmap(100, 25);
5![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
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System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(img);
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System.Drawing.Font fnt = new System.Drawing.Font("Arial", 12, System.Drawing.FontStyle.Regular);
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System.Drawing.Brush brsh = System.Drawing.Brushes.Black;
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System.Drawing.Pen pn = new System.Drawing.Pen(System.Drawing.Color.Black, 0);
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g.Clear(System.Drawing.Color.FromArgb(255, 255, 255));
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g.DrawString(strNum, fnt, brsh, 2, 2);
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//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
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if (System.IO.File.Exists(@"E:\Carl\webTest\WebSite2\images\random.Gif"))
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System.IO.File.Delete(@"E:\Carl\webTest\WebSite2\images\random.Gif");
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img.Save(@"E:\Carl\webTest\WebSite2\images\random.Gif", System.Drawing.Imaging.ImageFormat.Gif);
17![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
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spRandomNum.InnerHtml = "<img src=\"images/random.Gif\" />";
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
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![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
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![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
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![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
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![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
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![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
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![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
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![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
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![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
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![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
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![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
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![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
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![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
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![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
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![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
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![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
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![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
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![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)