Linq表达式过滤实体的集合列表，并维护实体列表

Lets say we have:

让我们说:

public class Foo
{
    public long Id { get; set; }
    public string Name { get; set; }
    public ICollection<Bar> { get; set; }
}

public class Bar
{
    public long Id { get; set; }
    public int Age { get; set; }

    public virtual Foo { get; set; }
    public long FooId  { get; set; }
}
public class Foo
{