使用可枚举范围的Ravendb3.0索引

我在RavenDB 3.0 build 3599中有以下索引：

from pupil in docs.Pupils
from year in Enumerable.Range(pupil.BirthAcademicYear, 12)
select new {
    pupil.Upn,
    year
}

它失败，返回以下错误消息：

Cannot implicitly convert type 'object' to 'System.Collections.Generic.IEnumerable<object>'. An explicit conversion exists (are you missing a cast?)

这将导致以下错误：

'object' does not contain a definition for 'Cast'

---

将索引更改为：

from pupil in docs.Pupils
from year in Enumerable.Select(Enumerable.Range(pupil.BirthAcademicYear, 12), (Func<int,object>)(u=> u))
select new {
    pupil.Upn,
    year
}

---

这会导致异常：无法将类型为“d_ub8”的对象强制转换为类型为“System.Collections.Generic.IEnumerable`1[System.object]”。

from pupil in docs.Pupils
from year in Enumerable.Select(Enumerable.Range(pupil.BirthAcademicYear, 12), (Func<int,object>)(u=> u))
select new {
    pupil.Upn,
    year
}