Asp.net(C#)实现验证码功能

新建一个专门用来创建验证码图片的页面ValidateCode.aspx
它的后台cs文件代码如下：
PageLoad

private void Page_Load(object sender, System.EventArgs e)
int iwidth = (int)(checkCode.Length * 11.5);
System.Drawing.Bitmap image = new System.Drawing.Bitmap(iwidth, 20);
Graphics g = Graphics.FromImage(image);
Font f = new System.Drawing.Font("Arial", 10, System.Drawing.FontStyle.Bold);
Brush b = new System.Drawing.SolidBrush(Color.White);
//g.FillRectangle(new System.Drawing.SolidBrush(Color.Blue),0,0,image.Width, image.Height);
g.Clear(Color.Blue);
g.DrawString(checkCode, f, b, 3, 3);

Pen blackPen = new Pen(Color.Black, 0);
Random rand = new Random();
for (int i=0;i<5;i++)
int y = rand.Next(image.Height);
g.DrawLine(blackPen,0,y,image.Width,y);
}

System.IO.MemoryStream ms = new System.IO.MemoryStream();
image.Save(ms,System.Drawing.Imaging.ImageFormat.Jpeg);
Response.ClearContent();
Response.ContentType = "image/Jpeg";
Response.BinaryWrite(ms.ToArray());
g.Dispose();
image.Dispose();
}

//g.FillRectangle(new System.Drawing.SolidBrush(Color.Blue),0,0,image.Width, image.Height);
g.Clear(Color.Blue);
这两种方法都可以改变生成图片的背景颜色
下面那个for循环用来生成一些随机的水平线

在需要用到验证码的页面添加一个<asp:Image>控件即可，但是要把ImageUrl指向生成验证码的页面

<asp:Image Runat="server" ID="ImageCheck" ImageUrl="ValidateCode.aspx"></asp:Image>

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