Use .DefaultIfEmpty() to make a left join with LINQ.

A left join:

public IQueryable<Feline> GetOtherCats()
{
var q =	from c in DbContext.Cats.Where(c => c.Name != "Mango") from d in DbContext.Dogs.Where(d => d.Id == c.Enemy).DefaultIfEmpty() select new Feline() {    Name = c.Name,    RemainingNumberOfLives = c.RemainingNumberOfLives,    Enemy = c.Enemy == null ? null : d.Name };
return q;
}

 
 

This is contrast is an inner join:

public IQueryable<Feline> GetOtherCats()
{
var q =	from c in DbContext.Cats.Where(c => c.Name != "Mango") from d in DbContext.Dogs.Where(d => d.Id == c.Enemy) select new Feline() {    Name = c.Name,    RemainingNumberOfLives = c.RemainingNumberOfLives,    Enemy = d.Name };
return q;
}