public class Father
{
    public virtual void Say()
    {
        Console.WriteLine("Father Say");
    }
}
 
public class Son : Father
{
    public override void Say()
    {
        base.Say();
        Console.WriteLine("Son Say");
    }
}

Son s = new Son();
s.Say();

public class Father
{
    public string Name { get; set; }
    public Father()
    {
        Name = "Father";
    }
}
 
public class Son : Father
{
    public Son()
        : base()
    {
    }
}

Son s = new Son();