"tools": {
  "Microsoft.EntityFrameworkCore.Tools.DotNet": "1.0.0-preview3-final"
},

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

var hash = new HashSet<int>();
var duplicates = list.Where(i => !hash.Add(i));

var movies = new List<Movie>
{
    new Movie("Titanic", 1998, 4.5f),
    new Movie("The Fifth Element", 1997, 4.6f),
    new Movie("Terminator 2", 1991, 4.7f),
    new Movie("Avatar", 2009, 5),
    new Movie("Platoon", 1986, 4),
    new Movie("My Neighbor Totoro", 1988, 5)
};

var distinctRatings = movies.DistinctBy(movie => movie.Rating);

// Output:
// Titanic,The Fifth Element,Terminator 2,Avatar,Platoon