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)






{


string checkCode = CreateRandomCode(4);


Session["CheckCode"] = checkCode;


CreateImage(checkCode);


}

其中CreateRandomCode是自定义的函数，参数代表验证码位数


private string CreateRandomCode(int codeCount)






{


string allChar = "0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,W,X,Y,Z" ;


string[] allCharArray = allChar.Split(',');


string randomCode = "";


int temp = -1;




Random rand = new Random();


for(int i = 0; i < codeCount; i++)






{


if(temp != -1)






{


rand = new Random(i*temp*((int)DateTime.Now.Ticks));


}


int t = rand.Next(35);


if(temp == t)






{


return CreateRandomCode(codeCount);


}


temp = t;


randomCode += allCharArray[t];


}


return randomCode;


}

CreateImage也是一个自定义的函数，用于生成图


private void CreateImage(string checkCode)






{


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>