LINQ中的多个from子句

Question

How can this LINQ query expression be re-expressed with extension method calls?

public static List<Tuple<int, int>> Concat()
{
    return (from x in Enumerable.Range(1, 3)
           from y in Enumerable.Range(4, 3)
           select new Tuple<int, int>(x, y)).ToList();
}

Answer 1

return Enumerable.Range(1, 3).SelectMany(x => Enumerable.Range(4, 3)
           .Select(y => new Tuple<int, int>(x, y))).ToList();

Your version looks more readable :-)

Answer 2

Enumerable.Range(1, 3).SelectMany(
    i => Enumerable.Range(4, 3),
    (i, j) => new Tuple<int, int>(i, j)
).ToList();