关系）：

  IQueryable< Pet> personPets =（
 from p in db.Person 
其中p.ID == somePersonID 
 select p 
）.Single（）。Pets.AsQueryable（）; 
 

虽然我可能会用这种方式写一些变化：

  var personPets = 
 db.Person.Single（t => t.Id == somePersonId）.Pets.AsQueryable 
 

Obfuscated Scenario: A person has zero, one or many pets.

Using Linq to Sql, the need is to get an IQueryable list of pets for the given personID. Here's the poorly mangled/butchered/obfuscated portion of the ERD:

Code:

 public IQueryable<Pet> GetPersonPets(int personID)
    {
        var personPets= from p in Person
        where p.ID == somePersonID
        select p.Pets;

        return personPets; //fail
        // return (IQueryable<Pet>)personPets  //also fail
        // return personPets.AsQueryable<Pet>()  //also fail
    }

Exception Raised:

Cannot implicitly convert type 
'System.Collections.Generic.IEnumerable (System.Data.Linq.EntitySet(Pet))' 
to 'System.Linq.IQueryable(Pet)'. 
An explicit conversion exists (are you missing a cast?) 

Failed Attempts:

Direct casting didn't work: (IQueryable<MyType>)

Calling collection method AsQueryable didn't work: .AsQueryable<MyType>()

Question:

How can you cast the results of the LinqToSql query properly to IQueryable?

This works for me (with different tables of course, but same relationship):

IQueryable<Pet> personPets = (
   from p in db.Person
   where p.ID == somePersonID
   select p
).Single().Pets.AsQueryable();

Although I'd probably write it in some variation of this way:

var personPets = 
    db.Person.Single(t => t.Id == somePersonId).Pets.AsQueryable();