返回IQueryable<T>与IEnumerable<T>?有什么区别?
IQueryable<Customer> custs = from c in db.Customers
where c.City == "<City>"
select c;
IEnumerable<Customer> custs = from c in db.Customers
where c.City == "<City>"
select c;
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两者都会延迟执行,何时应该优先于另一个?