NET7下显示验证码

   public  class VierificationCodeServices
    {

        /// <summary>  
        /// 该方法用于生成指定位数的随机数  
        /// </summary>  
        /// <param name="VcodeNum">参数是随机数的位数</param>  
        /// <returns>返回一个随机数字符串</returns>  
        public  string RndNum(int VcodeNum)
        {
            //验证码可以显示的字符集合  
            string Vchar = "0,1,2,3,4,5,6,7,8,9,a,b,c,d,e,f,g,h,i,j,k,l,m,n,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,P,P,Q" +
                ",R,S,T,U,V,W,X,Y,Z";
            string[] VcArray = Vchar.Split(new Char[] { ',' });//拆分成数组   
            string code = "";//产生的随机数  
            int temp = -1;//记录上次随机数值，尽量避避免生产几个一样的随机数  

            Random rand = new Random();
            //采用一个简单的算法以保证生成随机数的不同  
            for (int i = 1; i < VcodeNum + 1; i++)
            {
                if (temp != -1)
                {
                    rand = new Random(i * temp * unchecked((int)DateTime.Now.Ticks));//初始化随机类  
                }
                int t = rand.Next(61);//获取随机数  
                if (temp != -1 && temp == t)
                {
                    return RndNum(VcodeNum);//如果获取的随机数重复，则递归调用  
                }
                temp = t;//把本次产生的随机数记录起来  
                code += VcArray[t];//随机数的位数加一  
            }
            return code;
        }

        /// <summary>  
        /// 该方法是将生成的随机数写入图像文件  nuget:Zkweb.system.drawing
        /// mac 下显示验证码还得 nuget:runtime.osx.10.10-x64.CoreCompat.System.Drawing
        /// </summary>  
        /// <param name="code">code是一个随机数</param>
        /// <param name="numbers">生成位数（默认4位）</param>  
        public MemoryStream CreateYZM(out string code, int numbers = 4)
        {
            code = RndNum(numbers);
            Bitmap Img = null;
            Graphics g = null;
            MemoryStream ms = null;
            Random random = new Random();
            //验证码颜色集合  
            Color[] c = { Color.Black, Color.Red, Color.DarkBlue, Color.Green, Color.Orange, Color.Brown, Color.DarkCyan, Color.Purple };

            //验证码字体集合
            string[] fonts = { "Verdana", "Microsoft Sans Serif", "Comic Sans MS", "Arial", "宋体" };


            //定义图像的大小，生成图像的实例  
            Img = new Bitmap((int)code.Length * 18, 32);

            g = Graphics.FromImage(Img);//从Img对象生成新的Graphics对象    

            g.Clear(Color.White);//背景设为白色  

            //在随机位置画背景点  
            for (int i = 0; i < 100; i++)
            {
                int x = random.Next(Img.Width);
                int y = random.Next(Img.Height);
                g.DrawRectangle(new Pen(Color.LightGray, 0), x, y, 1, 1);
            }
            //验证码绘制在g中  
            for (int i = 0; i < code.Length; i++)
            {
                int cindex = random.Next(7);//随机颜色索引值  
                int findex = random.Next(5);//随机字体索引值  
                Font f = new Font(fonts[findex], 15, FontStyle.Bold);//字体  
                Brush b = new SolidBrush(c[cindex]);//颜色  
                int ii = 4;
                if ((i + 1) % 2 == 0)//控制验证码不在同一高度  
                {
                    ii = 2;
                }
                g.DrawString(code.Substring(i, 1), f, b, 3 + (i * 12), ii);//绘制一个验证字符  
            }
            ms = new MemoryStream();//生成内存流对象  
            Img.Save(ms, ImageFormat.Jpeg);//将此图像以Png图像文件的格式保存到流中  

            //回收资源  
            g.Dispose();
            Img.Dispose();
            return ms;
        }

    }

//注入
 builder.Services.AddSingleton<Util.VierificationCodeServices>(new Util.VierificationCodeServices());
 
 //html使用
 <img id="imgcode" src="/Home2/Genyzm" onclick="changecode()" />
 
 //控制器后端代码，需要用到session，记得nuget包，不过好像NET7中把那个NUGET包废弃了，但还能用
  /// <summary>
        /// 图形验证码
        /// </summary>
        /// <returns></returns>
        public IActionResult GenYZM([FromServices] VierificationCodeServices _vierificationCodeServices)
        {
            string code = "";
            System.IO.MemoryStream ms = _vierificationCodeServices.CreateYZM(out code);
            HttpContext.Session.SetString("Code", code);
            Response.Body.Dispose();
            return File(ms.ToArray(), @"image/png");
        }