using System;

using System.Linq;

public class Program

{

    public static void Main()

    {

        var list = new[]

            {

                new { id = 3, Name = "", Location = "LocationA" },

                new { id = 2, Name = "", Location = "LocationA" },

                new { id = 1, Name = "T", Location = "LocationB" },

                new { id = 2, Name = "H", Location = "LocationB" },

                new { id = 3, Name = "E", Location = "LocationB" },

                new { id = 3, Name = "R", Location = "LocationB" },

                new { id = 5, Name = "U", Location = "LocationC" },

                new { id = 5, Name = "S", Location = "LocationC" },

                new { id = 5, Name = "S", Location = "LocationD" },

                new { id = 4, Name = "O", Location = "LocationD" },

                new { id = 4, Name = "Z", Location = "LocationE" },

            };

        var query1 = list

            .Where(s => s.Name != "")

            .GroupBy(g => new { g.Location, g.id })

            .Where(g => g.Count() > 1)

            .SelectMany(g => g)

​

            .ToList();

        Console.WriteLine("output\n" + string.Join("\n", query1));

    }

}