asp.net 生成验证码

1.添加一个.ashx文件

public void ProcessRequest(HttpContext context)

{

//context.Response.ContentType = "text/plain";

//context.Response.Write("Hello World");

string g = GenerateCheckCode();

CreateCheckCodeImage(g);

}

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 % 3 == 0)

{

//生成'0'-'9'字符

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

}

else if (number % 3 == 1)

{

//生成'A'-'Z'字符

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

}

else

{

//生成'a'-'z'字符

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

}

checkCode += code.ToString();

}

HttpContext.Current.Response.Cookies.Add(new HttpCookie("checkcode", checkCode));

return checkCode;

//两个字符相加等于=asicc码加

}

private void CreateCheckCodeImage(string checkCode)

{

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

return;

//(int)Math.Ceiling((checkCode.Length * 12.5)),22

System.Drawing.Bitmap image = new System.Drawing.Bitmap(80, 30);

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 < 5; i++)

{

int x1 = random.Next(image.Width + 10);

int x2 = random.Next(image.Width + 10);

int y1 = random.Next(image.Height + 10);

int y2 = random.Next(image.Height + 10);

Pen p = new Pen(Color.Gray, 4);

g.DrawLine(p, x1, y1, x2, y2);

}

Font font = new System.Drawing.Font("Arial", 15, (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.Blue, System.Drawing.Color.DarkRed, 1.2f, true);

g.DrawString(checkCode, font, brush, 5, 5);

//画图片的前景噪音点

for (int i = 0; i < 200; i++)

{

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

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

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

}

//画图片的边框线

g.DrawRectangle(new System.Drawing.Pen(System.Drawing.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);

HttpContext.Current.Response.ClearContent();

HttpContext.Current.Response.ContentType = "image/jpg";

HttpContext.Current.Response.BinaryWrite(ms.ToArray());

}

finally

{

g.Dispose();

image.Dispose();

}

}

public bool IsReusable

{

get

{

return false;

}

}

2.在用到验证码的界面添加一个img控件，并且src属性指向.ashx文件

<img alt="看不清，换一张" src="CheckCode.ashx" onclick="this.src='CheckCode.ashx?abc='+Math.random()" />

3.提交后先判断验证码是否正确

//检查验证码是否正确

if(this.txt_checkcode.Text.ToLower ()!=this.Request.Cookies["checkcode"].Value.ToLower () )

{

//写脚本提示

if( this.ClientScript.IsStartupScriptRegistered ("checkcode")==false)

{

this.ClientScript.RegisterStartupScript(this.GetType (),"checkcode","<script>alert('验证码错误!');</script>");

}

return;

}