验证码生成

public class ValidCode
{
public enum CodeType { Words, Numbers, Characters, Alphas }

    private const double PI = 3.1415926535897932384626433832795;
    private const double PI2 = 6.283185307179586476925286766559;

    private int _len;
    private CodeType _codetype;
    private readonly Single _jianju = (float)18.0;
    private readonly Single _height = (float)24.0;
    private string _checkCode;

    public string CheckCode
    {
        get
        {
            return _checkCode;
        }
    }

    private string returnCode = "";

    public string ReturnCode
    {
        get
        {
            return returnCode;
        }

        set
        {
            returnCode = value;
        }
    }
    /// <summary>
    /// 构造函数
    /// </summary>
    /// <param name="len">验证码长度</param>
    /// <param name="ctype">验证码类型：字母、数字、字母+数字</param>
    public ValidCode(int len, CodeType ctype)
    {
        this._len = len;
        this._codetype = ctype;
    }

    private string GenerateNumbers()
    {
        Random random = new Random();
        for (int i = 0; i < _len; i++)
        {
            string num = Convert.ToString(random.Next(10000) % 10);
            ReturnCode += num;
        }
        return ReturnCode.Trim();
    }

    private string GenerateCharacters()
    {
        string num = "";
        Random random = new Random();
        for (int i = 0; i < _len; i++)
        {
            if (random.Next(500) % 2 == 0)
            {
                num = Convert.ToString((char)(65 + random.Next(10000) % 26));
            }
            else
            {
                num = Convert.ToString((char)(97 + random.Next(10000) % 26));
            }
            ReturnCode += num;
        }
        return ReturnCode.Trim();
    }

    private string GenerateAlphas()
    {
        string num = "";
        Random random = new Random();
        for (int i = 0; i < _len; i++)
        {
            if (random.Next(500) % 3 == 0)
            {
                num = Convert.ToString(random.Next(10000) % 10);
            }
            else if (random.Next(500) % 3 == 1)
            {
                num = Convert.ToString((char)(65 + random.Next(10000) % 26));
            }
            else
            {
                num = Convert.ToString((char)(97 + random.Next(10000) % 26));
            }
            ReturnCode += num;
        }
        return ReturnCode.Trim();
    }

    /// <summary>
    /// 背景
    /// </summary>
    /// <param name="srcBmp"></param>
    /// <param name="bXDir"></param>
    /// <param name="dMultValue"></param>
    /// <param name="dPhase"></param>
    /// <returns></returns>
    private Bitmap TwistImage(Bitmap srcBmp, bool bXDir, double dMultValue, double dPhase)
    {
        Bitmap destBmp = new Bitmap(srcBmp.Width, srcBmp.Height);
        //将位图背景填充为白色
        Graphics graph = Graphics.FromImage(destBmp);
        graph.FillRectangle(new SolidBrush(System.Drawing.Color.White), 0, 0, destBmp.Width, destBmp.Height);
        graph.Dispose();

        double dBaseAxisLen = bXDir ? (double)destBmp.Height : (double)destBmp.Width;
        for (int i = 0; i < destBmp.Width; i++)
        {
            for (int j = 0; j < destBmp.Height; j++)
            {
                double dx = 0;
                dx = bXDir ? (PI2 * (double)j) / dBaseAxisLen : (PI2 * (double)i) / dBaseAxisLen;
                dx += dPhase;
                double dy = Math.Sin(dx);

                //取得当前点的颜色
                int nOldX = 0, nOldY = 0;
                nOldX = bXDir ? i + (int)(dy * dMultValue) : i;
                nOldY = bXDir ? j : j + (int)(dy * dMultValue);

                System.Drawing.Color color = srcBmp.GetPixel(i, j);
                if (nOldX >= 0 && nOldX < destBmp.Width && nOldY >= 0 && nOldY < destBmp.Height)
                {
                    destBmp.SetPixel(nOldX, nOldY, color);
                }
            }
        }
        return destBmp;
    }

    /// <summary>
    /// 
    /// </summary>
    /// <returns></returns>
    public Stream CreateCheckCodeImage()
    {
        ReturnCode = "";
        string checkCode;
        switch (_codetype)
        {
            case CodeType.Alphas:
                checkCode = GenerateAlphas();
                break;
            case CodeType.Numbers:
                checkCode = GenerateNumbers();
                break;
            case CodeType.Characters:
                checkCode = GenerateCharacters();
                break;
            default:
                checkCode = GenerateAlphas();
                break;
        }
        this._checkCode = checkCode;
        MemoryStream ms = null;

        if (checkCode == null || checkCode.Trim() == string.Empty)
            return null;
        Bitmap image = new Bitmap((int)Math.Ceiling((checkCode.Length * _jianju)), (int)_height);
        Graphics g = Graphics.FromImage(image);

        try
        {
            Random random = new Random();
            g.Clear(Color.White);
            //画图片的背景噪音线

            for (int i = 0; i < 18; 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.FromArgb(random.Next()), 1), x1, y1, x2, y2);
            }

            Font font = new Font("Times New Roman", 14, FontStyle.Bold);
            LinearGradientBrush brush = new LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.DarkRed, 1.2f, true);
            if (_codetype != CodeType.Words)
            {
                for (int i = 0; i < checkCode.Length; i++)
                {
                    g.DrawString(checkCode.Substring(i, 1), font, brush, 2 + i * _jianju, 1);
                }
            }
            else
            {
                g.DrawString(checkCode, font, brush, 2, 2);
            }

            //画图片的前景噪音点
            for (int i = 0; i < 150; i++)
            {
                int x = random.Next(image.Width);
                int y = random.Next(image.Height);
                image.SetPixel(x, y, Color.FromArgb(random.Next()));
            }

            //画图片的波形滤镜效果
            if (_codetype != CodeType.Words)
            {
                image = TwistImage(image, true, 3, 1);
            }

            //画图片的边框线
            g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);

            ms = new MemoryStream();
            image.Save(ms, ImageFormat.Gif);
        }
        finally
        {
            g.Dispose();
            image.Dispose();
        }
        return ms;
    }
}

WPF界面调用

  ValidCode validCode = new ValidCode(4, ValidCode.CodeType.Alphas);
  image1.Source = BitmapFrame.Create(validCode.CreateCheckCodeImage());

Winform界面调用
ValidCode validCode = new ValidCode(4, ValidCode.CodeType.Alphas);
Bitmap bitmap = new Bitmap(validCode.CreateCheckCodeImage());