using System;

using System.Linq;

public class Program

{

    public static void Main()

    {

        var Array1 = new[] { (id: 123, name: "abc"), (id: 456, name: "def"), (id: 123, name: "ghi") };

        var Array2 = new[] { (id: 123, name: "abc"), (id: 456, name: "def") };

        var query = 

            from a1 in Array1.Where(x => Array1.Count(y => y.id == x.id) == 1)

            join a2 in Array2.Where(x => Array2.Count(y => y.id == x.id) == 1)

                on a1.id equals a2.id

            select (a1, a2);

​

        foreach (var x in query)

        {

            Console.WriteLine($"{x.a1} {x.a2}");

        }

    }

}