namespace Blog
{
/// <summary>
/// CheckCode 的摘要说明。
/// </summary>
public class CheckCode : System.Web.UI.Page
{
private void Page_Load(object sender, System.EventArgs e)
{
// 在此处放置用户代码以初始化页面
this.CreateCheckCodeImage(GenerateCheckCode());//验证码
}

#region Web 窗体设计器生成的代码
override protected void OnInit(EventArgs e)
{
//
// CODEGEN: 该调用是 ASP.NET Web 窗体设计器所必需的。
//
InitializeComponent();
base.OnInit(e);
}

/// <summary>
/// 设计器支持所需的方法 - 不要使用代码编辑器修改
/// 此方法的内容。
/// </summary>
private void InitializeComponent()
{   
this.Load += new System.EventHandler(this.Page_Load);
}
#endregion

private string GenerateCheckCode()
{
int number;
char code;
string checkCode = String.Empty;

System.Random random = new Random();

for (int i = 0; i < 5; i++)
{
number = random.Next();

if (number % 2 == 0)
code = (char)('0' + (char)(number % 10));
else
code = (char)('A' + (char)(number % 26));

checkCode += code.ToString();
}

Session["CheckCode"] = checkCode.ToLower(); //一般放在Session

里不要放在Cookie里

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 * 21.0)), 25);
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.Wheat);

//画图片的背景噪音线
for (int i = 0; i < 50; 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.Tan), x1, y1, x2,

y2);
}

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

random.Next(18,23), (System.Drawing.FontStyle.Bold |

System.Drawing.FontStyle.Italic));
System.Drawing.Drawing2D.LinearGradientBrush brush =

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

image.Height), Color.Orange,Color.SteelBlue, 1.2f, true);
g.DrawString(checkCode, font, brush, 2, -3);

//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);

System.IO.MemoryStream ms = new

System.IO.MemoryStream();
image.Save(ms,

System.Drawing.Imaging.ImageFormat.Gif);
Response.ClearContent();
Response.ContentType = "image/Gif";
Response.ExpiresAbsolute = DateTime.Now.Add(new

TimeSpan(-1, 0, 0, 0));
Response.BinaryWrite(ms.ToArray());
}
finally
{
g.Dispose();
image.Dispose();
}
}
}
}