No. Try this:
using System;
public class A
{
public void x()
{
Console.WriteLine("A:x");
}
}
public class B : A
{
public new void x()
{
Console.WriteLine("B:x");
}
}
public class Program
{
public static void Main()
{
A a = new B();
a.x();
}
}
If hiding was polymorphic,
B:x
would have been printed.