public abstract class ValueObject
{
    public override bool Equals(object obj)
    {
        if (ReferenceEquals(obj, null))
        {
            return false;
        }

        return StructuralComparer.AreEqual(this, obj);
    }

    public override int GetHashCode()
    {
        return StructuralHashCodeCalculator.CalculateHashCode(this);
    }

    public static bool operator ==(ValueObject a, ValueObject b)
    {
        if (ReferenceEquals(a, null) && ReferenceEquals(b, null))
        {
            return true;
        }

        if (ReferenceEquals(a, null) || ReferenceEquals(b, null))
        {
            return false;
        }

        return a.Equals(b);
    }

    public static bool operator !=(ValueObject a, ValueObject b)
    {
        return !(a == b);
    }
}