Question

Looks like join cannot use sets defined inside query or am I doing something wrong?

from a in new[] {
    new { Id = 1 },
    new { Id = 2 } }

let bees = new[] {
    new { Id = 2 },
    new { Id = 3 } }

join b in bees on a.Id equals b.Id

select 1;

This one gives compile time error ‘Element “bees” does not exist in the current context.’ What’s wrong with the query?

Answer 1

This is not legal either way you slice it – you cannot declare a range variable “in the middle” of a join – internally the let clause gets translated to a Select() statement with an anonymous type – but you cannot use Select() either in the middle of the join, you have to move it after the join.