验证码

==========

<script type="text/javascript">
function getVCode()
{
    var vcode = document.getElementById("vcode");
    vcode.src = "../ValidateCode/ValidateCodeTest.ashx?i=" + Math.random();
}
</script>

<div class="form-group">
    <input type="text" class="form-control input-lg" name="txtvcode" placeholder="请输入验证码"
    required style="200px;" />
    @*
    <img src="ValidateCode/ValidateCodeTest.ashx" alt="验证码" id="YanZen" />
    <a href="javascript:CetCode()">
        看不清换一张
    </a>
    *@
    <img src="../ValidateCode/ValidateCodeTest.ashx" id="vcode" align="middle"
    alt="看不清，换一张" onclick="getVCode()" />
    <a href="javascript:getVCode()" class="hyz">
        换一张
    </a>
</div>

HttpCookie cookie = Request.Cookies["CheckCode"];
string coo = cookie.Value;
string vcode = Request.Form["txtvcode"]; === = == == = ===
/// <summary>
/// ValidateCodeTest 的摘要说明
/// </summary>
public class ValidateCodeTest: IHttpHandler
{
    public void ProcessRequest(HttpContext context)
    {
        context.Response.ContentType = "text/plain";
        //context.Response.Write("Hello World");
        context.Response.Cache.SetCacheability(HttpCacheability.NoCache); ///特别注意，如不加，单击验证图片’看不清换一张’，无效果．
        this.CreateCheckCodeImage(GenerateCheckCode(context), context);
    }
    private string GenerateCheckCode(HttpContext context)
    {
        int number;
        char code;
        string checkCode = String.Empty;
        System.Random random = new Random();
        for(int i = 0; i < 6; i++)
        {
            number = random.Next();
            if(number % 2 == 0) code = (char)('0' + (char)(number % 10));
            else if(number % 3 == 0) code = (char)('A' + (char)(number % 26));
            else code = (char)('a' + (char)(number % 26));
            checkCode += code.ToString();
        }
        context.Response.Cookies.Add(new HttpCookie("CheckCode", checkCode)); //你也可以存到Seesion里．
        return checkCode;
    }
    private void CreateCheckCodeImage(string checkCode, HttpContext context)
    {
        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 < 25; 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.Silver), x1, y1, x2, y2);
            }
            Font font = new System.Drawing.Font("Arial", 12, (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, Color.DarkRed, 1.2 f, 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);
            System.IO.MemoryStream ms = new System.IO.MemoryStream();
            image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
            context.Response.ClearContent();
            context.Response.ContentType = "image/Gif";
            context.Response.BinaryWrite(ms.ToArray());
        }
        finally
        {
            g.Dispose();
            image.Dispose();
        }
    }
    public bool IsReusable
    {
        get
        {
            return false;
        }
    }
}