随机生成图片验证码

---ValidationCodeImg.aspx

<%@ import namespace="System"%>
<%@ import namespace="System.IO"%>
<%@ import namespace="System.Drawing"%>
<%@ import namespace="System.Drawing.Imaging"%>
<%@ import namespace="System.Drawing.Drawing2D"%>
<script language="C#" runat="server">
private Bitmap validateimage;
private Graphics g;
public void Page_Load(object Sender ,EventArgs e )
{
if (!IsPostBack)
{
string VNum =MakeValidateCode( );
Session["VNum"]=VNum;
ValidateCode(VNum);
}
}

public void ValidateCode(string VNum)
{
validateimage = new Bitmap(70, 20, PixelFormat.Format24bppRgb);
g = Graphics.FromImage(validateimage);

g.DrawString(VNum, new Font("Verdana",15),new SolidBrush(Color.White),new PointF(8,0));
g.FillRectangle(new LinearGradientBrush(new Point(0,0), new Point(110,20), Color.FromArgb(0,0,0,0),Color.FromArgb(255,255,60,40)),0,0,120,30);
g.Save();
MemoryStream ms=new MemoryStream();
validateimage.Save(ms,System.Drawing.Imaging.ImageFormat.Gif);
Response.ClearContent();
Response.ContentType="image/gif";
Response.BinaryWrite(ms.ToArray());
Response.End();
}

string MakeValidateCode()
{
char[] s = new char[]{'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','v','w','x','y','z','A','B','C','D','E','F','G' ,'H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W' ,'X','Y','Z'};
string num = "";
Random r = new Random();
for(int i = 0; i < 5; i++)
{
num += s[r.Next(0, s.Length)].ToString();
}
return num;
}

---ShowValidationCodeImg.aspx

<asp:Image id="Image1" runat="server" ImageUrl="ValidationCodeImg.aspx"></asp:Image>

使用方法

现在，已经生成了图片验证码，在需要进行验证时，将MakeValidateCode()生成的字符串传递给相应的验证函数即可。