ASP.NET----検証コード類

using System.Collections.Generic;
using System.IO;
using System.Drawing;
using System.Text;
using System;

namespace Core.Common.Tool
{
    /// <summary>
    ///               
    /// </summary>
    public static class ValidateCode
    {
        #region     

        /// <summary>
        ///      
        /// </summary>
        /// <returns>   </returns>
        public static string CreateValidateCode()
        {
            int number;
            char code;
            string verifyCode = string.Empty;

            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));

                verifyCode += code.ToString();
            }

            return verifyCode;
        }

        /// <summary>
        ///        
        /// </summary>
        /// <param name="validateCode">   </param>
        /// <returns>     </returns>
        public static Bitmap CreateValidateCodeImage(string validateCode)
        {
            if (validateCode == null || validateCode.Trim() == String.Empty)
                return null;

            Bitmap image = new Bitmap((int)Math.Ceiling((validateCode.Length * 12.5)), 22);
            Graphics g = Graphics.FromImage(image);

            try
            {
                Random random = new Random();

                g.Clear(Color.White);

                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 Font("Arial", 12, (FontStyle.Bold | FontStyle.Italic));
                System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.DarkRed, 1.2f, true);
                g.DrawString(validateCode, font, brush, 2, 2);

                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()));
                }

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

                return image;
            }
            catch
            {
                return null;
            }
            finally
            {
                g.Dispose();
                image.Dispose();
            }
        }

        /// <summary>
        ///        
        ///       （GIF  ）
        /// </summary>
        /// <param name="validateCode">   </param>
        /// <param name="validateCodeFilePath">    （     ）</param>
        /// <returns>      </returns>
        public static bool CreateValidateCodeImage(string validateCode, string validateCodeFilePath)
        {
            if (validateCode == null || validateCode.Trim() == String.Empty)
                return false;

            Bitmap image = new Bitmap((int)Math.Ceiling((validateCode.Length * 12.5)), 22);
            Graphics g = Graphics.FromImage(image);

            try
            {
                Random random = new Random();

                g.Clear(Color.White);

                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 Font("Arial", 12, (FontStyle.Bold | FontStyle.Italic));
                System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.DarkRed, 1.2f, true);
                g.DrawString(validateCode, font, brush, 2, 2);

                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()));
                }

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

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

                return true;
            }
            catch
            {
                return false;
            }
            finally
            {
                g.Dispose();
                image.Dispose();
            }
        }

        #endregion
    }
}