asp.net生成随机数或字母验证码代码

///建CheckCode.aspx

///在用的地方 <asp:Image ID="Image1" runat="server" Height="27px" Width="77px"

imageurl="CheckCode.aspx"/>

using System;

using System.Collections;

using System.Configuration;

using System.Data;

using System.Linq;

using System.Web;

using System.Web.Security;

using System.Web.UI;

using System.Web.UI.HtmlControls;

using System.Web.UI.WebControls;

using System.Web.UI.WebControls.WebParts;

using System.Xml.Linq;

using System.Drawing;

public partial class CheckCode : System.Web.UI.Page

{

protected void Page_Load(object sender, EventArgs e)

{

CreateCheckCodeImage(GenerateCheckCode());

}

private string GenerateCheckCode() //绘制4个随机数或字母

{

int number;

char code;

string checkCode = String.Empty;

Random random = new Random();

for (int i = 0; i < 4; i++)

{

number = random.Next();

if (number % 2 == 0)

code = (char)('0' + (char)(number % 10));

else

code = (char)('A' + (char)(number % 26));

checkCode += code.ToString();

}

Response.Cookies.Add(new HttpCookie("CheckCode", checkCode));

return checkCode;

}

private void CreateCheckCodeImage(string checkCode)

{

if (checkCode == null || checkCode.Trim() == String.Empty)

return;

System.Drawing.Bitmap image = new

System.Drawing.Bitmap((int)Math.Ceiling((checkCode.Length * 12.5)), 22);

Graphics g = Graphics.FromImage(image);

try

{

//生成随机生成器

Random random = new Random();

//清空图片背景色

g.Clear(Color.White);

//画图片的背景噪音线

for (int i = 0; i < 2; i++)

{

int x1 = random.Next(image.Width);

int x2 = random.Next(image.Width);

int y1 = random.Next(image.Height);

int y2 = random.Next(image.Height);

g.DrawLine(new Pen(Color.Black), x1, y1, x2, y2);

}

Font font = new System.Drawing.Font("Arial", 12,

(System.Drawing.FontStyle.Bold));

System.Drawing.Drawing2D.LinearGradientBrush brush = new

System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(0, 0, image.Width,

image.Height), Color.Blue, Color.DarkRed, 1.2f, true);

g.DrawString(checkCode, font, brush, 2, 2);

//画图片的前景噪音点

for (int i = 0; i < 100; i++)

{

int x = random.Next(image.Width);

int y = random.Next(image.Height);

image.SetPixel(x, y, Color.FromArgb(random.Next()));

}

//画图片的边框线

g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1,

image.Height - 1);

//输出到浏览器

System.IO.MemoryStream ms = new System.IO.MemoryStream();

image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);

Response.ClearContent();

Response.ContentType = "image/Gif";

Response.BinaryWrite(ms.ToArray());

}

finally

{

g.Dispose();

image.Dispose();

}

}

}