System.Collections.Generic.List <Plate>「不包含定義‘時間’並沒有擴展方法‘時間’

Question

下面是我試圖執行

var usersQuery = 
from user in Model.Users 
select user.Plates; 

var platesQuery = 
from plate in usersQuery 
group plate by plate.Time into grouping 
select grouping; 

我收到以下錯誤LINQ聲明

System.Collections.Generic.List<AllYourPlates.Domain.Entities.Plate>' does not contain a definition for 'Time' and no extension method 'Time' accepting a first argument of type 'System.Collections.Generic.List<AllYourPlates.Domain.Entities.Plate>' could be found (are you missing a using directive or an assembly reference? 

我找不出什麼問題。

Answer 1

usersQuery是IEnumerable<IEnumerable<Plate>>您可以糾正這種在platesQuery這樣的：

var platesQuery = from plates in usersQuery 
        from plate in plates 
        group plate by plate.Time into grouping 
        select grouping; 

或者變平的初步結果，所以你有一個IEnumerable<Plate>代替：

var usersQuery = from user in Model.Users 
       from plate in user.Plates 
       select plate;