LINQ is amazing, but only if I don't need to do left / right outer join, the solution to use the DefaultIfEmpty() method looks weird.
I wish if C# could extend it keywords to add "leftjoin", "rightjoin" so that I can simply code as following:

var q = from c in db.Categories
            leftjoin p in db.Products on c.CategoryID equals p.CategoryID
            select new 
            {
                     p.ProductName, 
                     c.CategoryName
            }