public abstract class ParentClass

{

    protected abstract ParentField Field {get;}

}

​

public class ChildClass : ParentClass

{

    public ChildClass(ChildField field) => Field = field;

    protected override ChildField Field {get;}

}

​

public class ParentField{}

public class ChildField : ParentField{}

​

public class Program

{

    public static void Main()

    {

        var child = new ChildClass(new ChildField());

    }

}