.NET (Core and Framework)

<br />
public class X1 {<br />
    //Various Properties<br />
    public string propQ;<br />
    public string propW;<br />
}<br />
<br />
public class X2 : X1 {<br />
    //More Properties<br />
    public string propE;<br />
    public string propR;<br />
}<br />
<br />
public class A1 {<br />
    //Various Properties<br />
    public string prop1 {<br />
        get {return _prop1;}<br />
        set {_prop1 = value;}<br />
    }<br />
    protected string _prop1 = "";<br />
<br />
    //Collections<br />
    public List<x1> colOfX {<br />
        get {return _x;}<br />
    }<br />
    protected List<x1> _x = new List<x1>();<br />
}<br />
<br />
public class A2 : A1 {<br />
    //Other Properties<br />
    public string prop2 {<br />
        get {<br />
            return "";<br />
        }<br />
        set {<br />
        }<br />
    }<br />
<br />
    //Override Collections<br />
/*<br />
    //Wont compile because return type is different (even though it is a descendant)<br />
    public override List<x2> colOfX {<br />
        get {<br />
            return _x;<br />
        }<br />
    }<br />
    //Wont compile because _x cant be cast to List<x2><br />
    public new List<x2> colOfX {<br />
        get {<br />
            return _x;<br />
        }<br />
    }<br />
 */<br />
}<br />
</x2></x2></x2></x1></x1></x1>