我目前正在使用 C# Windows App Forms 做一个 ID pic 上传系统，我想允许用户上传图像，并且图像必须只包含 1 个正面。为了防止用户上传超过 1 张人脸，我想在系统检测到一张图像中的一张以上人脸时提示他们一条错误消息，但我不知道如何去做。我使用了竹内拓哉的 dlibdotnet 库。

这是我当前的代码。

namespace DetectTrial


{

    public partial class Form1 : Form
    {
        #region Fields
        private readonly BackgroundWorker _BackgroundWorker;
        #endregion

        #region Constructors
        public Form1()
        {
            this.InitializeComponent();
            this._BackgroundWorker = new BackgroundWorker();
            this._BackgroundWorker.DoWork += this.BackgroundWorkerOnDoWork;
        }
        #endregion

        #region Methods
        #region Event Handlers

        private void BackgroundWorkerOnDoWork(object sender,DoWorkEventArgs doWorkEventArgs)
        {
            var path = doWorkEventArgs.Argument as string;
            if (string.IsnullOrWhiteSpace(path) || !File.Exists(path))
                return;

            using (var faceDetector = Dlib.GetFrontalFaceDetector())
            using (var ms = new MemoryStream(File.ReadAllBytes(path)))
            using (var bitmap = (Bitmap)Image.FromStream(ms))
            {
                using (var image = bitmap.ToArray2D<RgbPixel>())
                {
                    var dets = faceDetector.Operator(image);
                    foreach (var g in dets)
                        Dlib.DrawRectangle(image,g,new RgbPixel { Green = 255 },thickness: 10);
                    var result = image.ToBitmap();
                    this.pictureBox1.Invoke(new action(() =>
                    {
                        this.pictureBox1.Image?.Dispose();
                        this.pictureBox1.Image = result;
                    }));

                }

            }

        }

        private void button1_Click(object sender,EventArgs e)
        {
            using (var opnfd = new OpenFileDialog())
            {
                opnfd.Filter = "Image Files (*.jpg;*.jpeg;*.png;)|*.jpg;*.jpeg;*.png";
                if (opnfd.ShowDialog(this) == DialogResult.OK)
                {
                    this._BackgroundWorker.RunWorkerAsync(opnfd.FileName);
                }
            }
        }
        #endregion
        #endregion
    }
}

我不知道从这里去哪里。