using System;

using System.Collections.Generic;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

        //Console.WriteLine("Hello World");

        var list = new List<int> { 1, 1, 2, 2, 3, 4 };

        var dupCount = list.GroupBy(x => x).Where(g => g.Count() > 1).Count();

        var dupCountQuery = (from item in list 

                            group item by item into grp

                            where grp.Count() > 1

                            select new {itemNew = grp.Count()}).Count();

        Console.WriteLine("Group Count: " + dupCount);

        Console.WriteLine("Group Count by Ling Query: " + dupCountQuery);

    }

}