Collections Data Structure C#

using System;
using System.Collections.Concurrent;
using System.Threading;
using System.Threading.Tasks;
class MainClass
{
        static void Main ()
        {
            ConcurrentStack cs = new ConcurrentStack();
            cs.Push(1);
            cs.Push(2);
            int result;
            cs.TryPeek(out result);
            cs.TryPop(out result);
            cs.Clear();
        }
}