Help regarding new modifier in C#

public class ClassA
{
public   void MethodNew()
{
Console.WriteLine("In MethodNew of ClassA");
}

public virtual void MethodOverride()
{
Console.WriteLine("In MethodOverride of ClassA");
}
}

    public class ClassB : ClassA
    {
        public new void MethodNew()
        {
            Console.WriteLine("In MethodNew of ClassB");
        }

        public override void MethodOverride()
        {
            Console.WriteLine("In MethodOverride of ClassB");
        }
    }
    class Program
    {
        static void Main(string[] args)
        {
            ClassA a = new ClassB();
            a.MethodNew();
            a.MethodOverride();
        }
    }