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

You can create extension method like:

public static IEnumerable LeftOuterJoin(this IEnumerable source, IEnumerable other, Func func, Func innerkey, Func res)
    {
        return from f in source
               join b in other on func.Invoke(f) equals innerkey.Invoke(b) into g
               from result in g.DefaultIfEmpty()
               select res.Invoke(f, result);
    }