C#生成随机验证码并验证其正确性

【实例截图】

 string allchar = ("0,1,2,3,4,5,6,7,8,9,a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z,A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z,");
            string[] cutallchar = allchar.Split(',');//以“,”分割字符串（allchar）
            string[] myfont = { "微软炭黑", "仿宋", "幼圆", "宋体", "隶书" };//为随机选中某一项做准备
            Color[] colors = { Color.Black, Color.Yellow, Color.Blue, Color.Purple, Color.Pink };//为随机选中某一项做准备
            Bitmap mybmp = new Bitmap(200, 50);//新建一个位图，大小为（200，50）
            Graphics mygps = Graphics.FromImage(mybmp);//新建一个Graphics类，里面有很多画图方法
            Random random = new Random();//新建随机数生成器
            Point point = new Point();//新建坐标点
            
            for (int i = 0; i < 5; i  )//开始画所选中的5个字符
            {
                int empt1 = random.Next(0, 62);
                record  = cutallchar[empt1];
                point.X = i * 30;
                point.Y = random.Next(0, 5);
                mygps.DrawString(cutallchar[empt1], new Font(myfont[random.Next(0, 4)], 30, FontStyle.Regular), new SolidBrush(colors[random.Next(0, 4)]), point);
                //Graphics.DrawString   Graphics类中画字符的方法：DrawString(String^, Font^, Brush^, PointF)在指定位置并且用指定的 Brush 和 Font 对象绘制指定的文本字符串。	

            }
            Point pointA = new Point();//开始画无规则的线，方法大致和上面一样
            Point pointB = new Point();
            for (int i = 0; i < 15; i  )
            {
                pointA.X = random.Next(0, mybmp.Width);
                pointA.Y = random.Next(0, mybmp.Height);
                pointB.X = random.Next(0, mybmp.Width);
                pointB.Y = random.Next(0, mybmp.Height);
                mygps.DrawLine(new Pen(colors[random.Next(0, 4)]), pointA, pointB);
            }

            Point pointt = new Point();//开始无规则画300个像素点 在我们新建的mybmp位图上
            for (int i = 0; i < 300; i  )
            {
                pointt.X = random.Next(0, mybmp.Width);
                pointt.Y = random.Next(0, mybmp.Height);
                mybmp.SetPixel(pointt.X, pointt.Y, colors[random.Next(0, 4)]);
            }
            pictureBox1.Image = mybmp;