私有静态列表是限制类实例集的适当方法吗

我试图避免使用相同的内部数据创建类的多个实例。我尝试了一个使用单独类来构建MCode的实现,但试图保护MCode构造函数没有起作用,所以我回到了这个实现。我想知道这是一个好的设计还是有更好的解决方案?

public class MCode : IEquatable<MCode>
{

    private readonly static List<MCode> Instances;
    public AEnum AE { get; }
    public byte C { get; }
    public BEnum BE { get; }

    public static MCode GetMCode(AEnum ae, BEnum be, byte c)
    {
            if (Instances==null)
            {
                Instances = new List<MCode>();
                var newmc = new MCode(ae, be, c);
                Instances.Add(newmc);
                return newmc;
            }

            var mc = Instances.Find(x => x.Equals(ae, be, c));

            if (mc == null)
            {
                var newmc = new MCode(ae, be, c);
                Instances.Add(newmc);
                return newmc;
            }
            return mc;
    }

    protected MCode(AEnum ae, BEnum be, byte c)
    {
        AE = ae;
        BE = be;
        C = c;
    }

    public new bool Equals(MCode mc)
    {
        return (GetHashCode() == mc.GetHashCode());
    }

    public new bool Equals(AEnum ae, BEnum be, byte c)
    {
        return (GetHashCode() == GetHashCode(ae, be, c));
    }

    public new int GetHashCode()
    {
        return ((byte)AE * 256 * 256 + (byte)BE * 256 * C);
    }

    public static int GetHashCode(AEnum ae, BEnum be, byte c)
    {
        return ((byte)ae * 256 * 256 + (byte)be * 256 * c);
    }
}