Method shadowing in C#

class A {
    public virtual void M() {
    }
}

class B : A {
    // Implicit shadowing. Not OK.
    // public void M() {
    // }

    // Override. Not shadowing. OK.
    // public override void M() {
    // }

    // Explicit shadowing. OK.
    public new void M() {
    }
}

public static class Program {
    public static void Main() {
    }
}