How do you perform a CROSS JOIN with LINQ to SQL?

问题

How do you perform a CROSS JOIN with LINQ to SQL?

回答1:

A cross-join is simply the Cartesian product of two sets. There's no explicit join operator for it.

var combo = from p in people
            from c in cars
            select new
            {
                p.Name,
                c.Make,
                c.Model,
                c.Colour
            };

回答2:

The same thing with linq extension methods:

var names = new string[] { "Ana", "Raz", "John" };
var numbers = new int[] { 1, 2, 3 };
var newList=names.SelectMany(
    x => numbers,
    (y, z) => { return y + z + " test "; });
foreach (var item in newList)
{
    Console.WriteLine(item);
}

回答3:

Based on Steve's answer, the simplest expression would be this:

var combo = from Person in people
            from Car    in cars
            select new {Person, Car};

回答4:

A Tuple is a good type for Cartesian product:

public static IEnumerable<Tuple<T1, T2>> CrossJoin<T1, T2>(IEnumerable<T1> sequence1, IEnumerable<T2> sequence2)
{
    return sequence1.SelectMany(t1 => sequence2.Select(t2 => Tuple.Create(t1, t2)));
}

回答5:

Extension Method:

public static IEnumerable<Tuple<T1, T2>> CrossJoin<T1, T2>(this IEnumerable<T1> sequence1, IEnumerable<T2> sequence2)
{
    return sequence1.SelectMany(t1 => sequence2.Select(t2 => Tuple.Create(t1, t2)));
}

And use like:

vals1.CrossJoin(vals2)

来源：https://stackoverflow.com/questions/56547/how-do-you-perform-a-cross-join-with-linq-to-sql