Linq to SQL - Many to Many Predicates - linq

Question

I'm familiar with doing simple Many-to-Many relationships (i.e. simple joins) in Linq to SQL, but I'm having a hard time thinking right now.
I have three tables (and so, entities in my Linq-to-SQL model) representing a taxonomic system. Standard-issue really:
Products - ProductTags - Tags
I'm writing a method that returns a set of Products where the Tag they're in matches a query. So if someone searches for "foo" then all products assigned with the tags "foobar" or "fooqux" (but not "bazbar") would be returned.
I know I have to structure the query into two parts: first to get the matching Tags, and then to get the Products that have those tags. It's the second part I'm stumped on.
Here's what I've got so far:
var tags = from t in db.Tags
where t.Name.Contains( tagSearchQuery )
select t;
var products = from p in db.Products
// then a miracle happens
select p;
Assistance much appreciated :)

Answer 1

You can do it in one query if you just start with the ProductTags table. You'll probably also need a Distinct to avoid duplicate products matching multiple tags.
var products = (from pt in db.ProductTags
where pt.Tag.Name.Contains( tagSearchQuery )
select pt.Product).Distinct();
or here's another way:
var products = from p in db.Products
from pt in p.ProductTags
where pt.Tag.Name.Contains( tagSearchQuery )
select p

Answer 2

IQueryable<Tag> tags =
from t in db.Tags
where t.Name.Contains( tagSearchQuery )
select t;
IQueryable<Product> products =
from p in db.Products
where p.ProductTags.Any(pt => tags.Contains(pt.Tag))
select p;
OR
IQueryable<Product> products =
from p in db.Products
from pt in p.ProductTags
let t = pt.Tag
where t.Name.Contains( tagSearchFragment )
group t by p into g
select g.Key;