public class Base
{
    public virtual void LogVirtual()
    {
        Console.WriteLine('LogVirtual Base');
    }

    public void Log()
    {
        Console.WriteLine('Log Base');
    }
}

public class Derivative
{
    public override void LogVirtual()
    {
        Console.WriteLine('LogVirtual Derivative');
    }

    public new void Log()
    {
        Console.WriteLine('Log Derivative');
    }
}

public class Test
{
    public void static Main()
    {
        Base base = new Base();
        Derivative derivative = new Derivative();
        var castedDeriv = (Base)derivative;

        base.Log(): //Log Base
        base.LogVirtual(); //LogVirtual Base

        derivative.Log(): //Log Derivative
        derivative.LogVirtual(); //LogVirtual Derivative

        castedDeriv.Log(): //Log Base
        castedDeriv.LogVirtual(); //LogVirtual Derivative

    }
}