深入c#绘制验证码的详解

1.使用一个picturebox空间，使用一个按钮，以刷新验证码。
2.首先定义checkcode()方法，以生成4为英文及数字组成的字符串序列：

private string checkcode()
        {
            int number;
            char code;
            string checkcode = string.empty;
            random random = new random();
            for (int i = 0; i < 4; i++)
            {
                number=random.next();
                if(number%2==0)
                    code=(char)('0'+(char)(number%10));
                else
                    code=(char)('a'+(char)(number%26));
                checkcode += " " + code.tostring();
            }
            return checkcode;
        }

3.自定义codeimage()方法，将checkcode()方法生成的序列转化为图片并显示：

        private void codeimage(string checkcode)
        {
            if (checkcode == null || checkcode.trim() == string.empty)
            {
                return;
            }
            system.drawing.bitmap image=new system.drawing.bitmap((int)math.ceiling((checkcode.length*50.0)),50);
            graphics g=graphics.fromimage(image);
            try
            {
                random random = new random();
                g.clear(color.white);
                for (int i = 0; i < 3; 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.black), x1, y1, x2, y2);
                }
                font font = new system.drawing.font("arial", 30, (system.drawing.fontstyle.bold));
                g.drawstring(checkcode, font, new solidbrush(color.red), 2, 2);
                for (int i = 0; i < 200; 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);
                this.picturebox1.width = image.width;
                this.picturebox1.height = image.height;
                this.picturebox1.backgroundimage = image;
            }
            catch
            {

            }
        }

4.

        private void form1_load(object sender, eventargs e)
        {
            codeimage(checkcode());
        }
        private void button1_click(object sender, eventargs e)
        {
            codeimage(checkcode());
        }