Nested “from” LINQ query expressed with extension methods

Question

How can I write this LINQ query by using the extension method syntax?

var query = from a in sequenceA
            from b in sequenceB
            select ...;         


        

Answer 1

var query = sequenceA.SelectMany(a => sequenceB.Select(b => ...));

Edit: as pointed out by Eric Lippert in the comments, this gives the same results, but is intentionally not how it is translated internally. See his answer for another way to call SelectMany, which does correspond to the original. Also, added the omitted b => for clarity.