var numbers1to10 = new[] {1,2,3,4,5,6,7,8,9,10}; var numbers5to15 = new[] {5,6,7,8,9,10,11,12,13,14,15}; var numbers5to10 = numbers1to10.Intersect(numbers5to15); Console.WriteLine(string.Join(",", numbers5to10)); //5,6,7,8,9,10