Base Domain Modelling classes

BaseEntity.cs

public abstract class Entity
{
  public virtual long Id { get; protected set; }
  protected virtual object Actual => this;

  public override bool Equals(object obj)
  {
    var other = obj as Entity;

    if (other is null)
      return false;

    if (ReferenceEquals(this, other))
      return true;

    if (Actual.GetType() != other.Actual.GetType())
      return false;

    if (Id == 0 || other.Id == 0)
      return false;

    return Id == other.Id;
  }

  public static bool operator ==(Entity a, Entity b)
  {
    if (a is null && b is null)
      return true;

    if (a is null || b is null)
      return false;

    return a.Equals(b);
  }

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

  public override int GetHashCode()
  {
    return (Actual.GetType().ToString() + Id).GetHashCode();
  }
}

ValueObject.cs

public abstract class ValueObject<T> where T : ValueObject<T>
{
  public override bool Equals(object obj)
  {
    var valueObject = obj as T;
 
    if (ReferenceEquals(valueObject, null))
      return false;
 
    return EqualsCore(valueObject);
  }
 
  protected abstract bool EqualsCore(T other);
 
  public override int GetHashCode()
  {
    return GetHashCodeCore();
  }
 
  protected abstract int GetHashCodeCore();
 
  public static bool operator ==(ValueObject<T> a, ValueObject<T> 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<T> a, ValueObject<T> b)
  {
    return !(a == b);
  }
}