C# 验证码的简单生成，登录实现校验验证码

登录实现校验验证码

1、思路：首先写一个生成验证码的接口，接口传出就是验证码的唯一id和验证码图片的base64， 把验证码的id当做缓存的key，再把生成的验证码code当做值存到缓存中。

2、登录：输入用户名、密码、验证码唯一id和用户输入的验证码值。用验证码唯一id获取到缓存中的验证码值，再和用户输入的值相比较。。就简单实现了

3、验证码生成代码

 public class VerifyCodeHelper
 {
     public static string BuildCode(out string code)
     {
         code = string.Empty; 7          Bitmap bitmap = new Bitmap(85, 30);//设置宽高
         Graphics graphics = Graphics.FromImage(bitmap);//生成画布
         graphics.Clear(Color.White);//清空画布

         string letters = "023456789abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNOPQRSTUVWXYZ";//去除 1 I l 
         Random random = new Random();
         //生成四位验证码
         for (int i = 0; i < 4; i++)
         {
             code += letters[random.Next(0, letters.Length)];
         }

         //画5条干扰线
         for (int i = 0; i < 5; i++)
         {
             int x1 = random.Next(bitmap.Width);
             int y1 = random.Next(bitmap.Height);
             int x2 = random.Next(bitmap.Width);
             int y2 = random.Next(bitmap.Height);
             graphics.DrawLine(new Pen(Color.Coral), x1, y1, x2, y2);
         }
         //画150个干扰点
         for (int i = 0; i < 150; i++)
         {
             int x1 = random.Next(bitmap.Width);
             int y1 = random.Next(bitmap.Height);
             bitmap.SetPixel(x1, y1, Color.FromArgb(random.Next()));//随机颜色填充
         }
         //画个边框
         graphics.DrawRectangle(new Pen(Color.Black), new Rectangle(0, 0, bitmap.Width - 1, bitmap.Height - 1));

         int randAngle = 45;//随机转动角度 //验证码旋转，防止机器识别
         char[] chars = code.ToCharArray();//拆散字符串成单字符数组
         //文字居中
         StringFormat format = new StringFormat(StringFormatFlags.NoClip);
         format.Alignment = StringAlignment.Center;
         format.LineAlignment = StringAlignment.Center;
         //定义颜色
         Color[] c = { Color.Black, Color.Red, Color.DarkBlue, Color.Green, Color.Orange, Color.Brown, Color.DarkCyan, Color.Purple };
         //定义字体
         string[] font = { "Verdana", "Microsoft Sans Serif", "Comic Sans MS", "Arial", "宋体" };
         for (int i = 0; i < chars.Length; i++)
         {
             int cindex = random.Next(7);
             int findex = random.Next(5);
             //字体样式(参数2为字体大小)
             Font f = new System.Drawing.Font(font[findex], 13, System.Drawing.FontStyle.Bold);
             Brush b = new System.Drawing.SolidBrush(c[cindex]);
             Point dot = new Point(16, 16);

             float angle = random.Next(-randAngle, randAngle);//转动的度数
             graphics.TranslateTransform(dot.X, dot.Y);//移动光标到指定位置
             graphics.RotateTransform(angle);
             graphics.DrawString(chars[i].ToString(), f, b, 1, 1, format);

             graphics.RotateTransform(-angle);//转回去
             graphics.TranslateTransform(2, -dot.Y);//移动光标到指定位置
         }
         string strbaser64 = string.Empty;
         using (System.IO.MemoryStream stream = new System.IO.MemoryStream())
         {
             bitmap.Save(stream, System.Drawing.Imaging.ImageFormat.Jpeg);
             byte[] arr = new byte[stream.Length];
             stream.Position = 0;
             stream.Read(arr, 0, (int)stream.Length);
             strbaser64 = Convert.ToBase64String(arr);
         }
         return strbaser64;
     }
 }