using System;

using System.Threading.Tasks;

public class Program

{

    public static void Main()

    {

        BaseClass myObj = new SuperClass();

        myObj.SomeProperty = 24;

        // can't set myObj.SomeHigherProperty!

        var superObj = myObj as SuperClass;

        superObj.SomeHigherProperty = "Hello world!";

    }

}

​

public class BaseClass

{

    public int SomeProperty { get; set; }

}

​

public class SuperClass : BaseClass

{

    public string SomeHigherProperty { get; set; }

}