c# – 为什么linq-to-sql查询被翻译成子查询？

(from c in Orders
select new 
{
   Id=c.Id,DeliveryDate = c.DeliveryDate.Value
}).Take(10)

被翻译成

SELECT TOP (10) [t1].[Id],[t1].[value] AS [DeliveryDate]
FROM (
    SELECT [t0].[Id],[t0].[DeliveryDate] AS [value]
    FROM [Orders] AS [t0]
    ) AS [t1]

但当我将DeliveryDate = c.DeliveryDate.Value更改为DeliveryDate = c.DeliveryDate时,SQL查询看起来很简单：

SELECT TOP (10) [t0].[Id],[t0].[DeliveryDate]
FROM [Orders] AS [t0]