继承和Linq-to-Entities

Question

我有以下模型：

public class Person 
{
    long Id;
    string name;
}

public class Student : Person
{
    string studentId;
}

public class Bus
{
    long Id;

    public ICollection<Person> riders {set; get;}
}

public class SchoolBus : Bus
{
    long schoolBusNumber;
}

我还有以下代码：

SchoolBus schoolBus = new SchoolBus();

schoolBus.riders = new List<Person>
{
    new Student { name = "Jim" },
    new Student { name = "Jane }
}


var query = from rider in SchoolBus.riders
    select new 
    {
        (rider as Student).studentId;
    }

Students和Person设置为单独的表，我使用的是DbContext。

我知道这不起作用的原因，但是有什么可能的解决方案让我使用Person集合来让它返回正确的studentId呢？

Answer 1

试试这个：

var studentIds = rider.OfType<Student>().Select(x => x.studentId);

Answer 2

如果您的代码与您所显示的完全相同，这将会起作用：

新的SchoolBus = schoolBus SchoolBus()；

schoolBus.riders = new List<Person>
{
    new Student { name = "Jim" },
    new Student { name = "Jane }
}
var query = from rider in SchoolBus.riders
select new 
{
    riderID = (rider as Student).studentId;
}

但是如果你的查询是在linq2entity上运行的，你应该显示你的确切代码和你的问题。