How do you perform a left outer join using linq extension methods

Question

Assuming I have a left outer join as such:

from f in Foo
join b in Bar on f.Foo_Id equals b.Foo_Id into g
from result in g.DefaultIfEmpty()
select new { Foo          


        

Answer 1

Turning Marc Gravell's answer into an extension method, I made the following.

internal static IEnumerable> LeftJoin(
    this IEnumerable left,
    IEnumerable right,
    Func selectKeyLeft,
    Func selectKeyRight,
    TRight defaultRight = default(TRight),
    IEqualityComparer cmp = null)
{
    return left.GroupJoin(
            right,
            selectKeyLeft,
            selectKeyRight,
            (x, y) => new Tuple>(x, y),
            cmp ?? EqualityComparer.Default)
        .SelectMany(
            x => x.Item2.DefaultIfEmpty(defaultRight),
            (x, y) => new Tuple(x.Item1, y));
}