如何在LINQ中進行分組？

Question

我需要返回特定用戶每天約會的最後30天，並檢查用戶是否每天至少進行8小時的約會。

在SQL我可以做到這一點與這個命令：

select IDAppointment,IDUser, SUM(DurationInHours) from Note where AppointmentDate > *lastmonth and IDUser = @userID group by IDUser,IDAppointment,AppointmentDate 

之後，我得到的結果和驗證DurationInHours（double類型）。

使用LINQ可以做到嗎？ 獲取上個月用戶預約的列表並日後驗證它

謝謝！

Answer 1

這應該是大致的，儘管這不在IDE的頭頂。

var result = context.Notes 
        .Where(n => [Your where clause]) 
        .GroupBy(n => new { n.IDUser, n.IDAppointment, n.AppointmentDate}) 
        .Select(g => new { 
            g.Key.IDAppointment, 
            g.Key.IDUser, 
            g.Sum(n => n.DurationInHours)}); 

UPDATE：

僅供參考您的where子句會是這樣的......（再次把我的頭頂部）

DateTime lastMonth = DateTime.Today.AddMonths(-1); 
int userId = 1 // TODO: FIX 
var result = context.Notes.Where(n => n.AppointmentDate > lastMonth 
            && n.IDUser = userId) 

從而造成....

DateTime lastMonth = DateTime.Today.AddMonths(-1); 
int userId = 1 // TODO: FIX 
var result = context.Notes 
        .Where(n => n.AppointmentDate > lastMonth 
          && n.IDUser = userId) 
        .GroupBy(n => new { n.IDUser, n.IDAppointment, n.AppointmentDate}) 
        .Select(g => new { 
            g.Key.IDAppointment, 
            g.Key.IDUser, 
            g.Sum(n => n.DurationInHours)}); 

Answer 2

這是我測試過的解決方案。

DateTime lastMonth = DateTime.Today.AddMonths(-1); 
int selectedUserId = 2; 

var notes = new List<Note>(
    new Note[] { 
     new Note() { 
      AppointmentDate = new DateTime(2013,7,30){}, 
      IDAppointment = 1, IDUser = 1, DurationInHours = 1 
     }, 
     new Note() { 
      AppointmentDate = new DateTime(2013,7,30){}, 
      IDAppointment = 1, IDUser = 1, DurationInHours = 2 
     }, 
     new Note() { 
      AppointmentDate = new DateTime(2013,7,30){}, 
      IDAppointment = 1, IDUser = 1, DurationInHours = 3 
     }, 
     new Note() { 
      AppointmentDate = new DateTime(2013,7,28){}, 
      IDAppointment = 2, IDUser = 2, DurationInHours = 2 
     }, 
     new Note() { 
      AppointmentDate = new DateTime(2013,7,28){}, 
      IDAppointment = 2, IDUser = 2, DurationInHours = 3 
     }, 
     new Note() { 
      AppointmentDate = new DateTime(2013,7,27){}, 
      IDAppointment = 2, IDUser = 2, DurationI nHours = 4 
     }, 
     new Note() { 
      AppointmentDate = new DateTime(2013,7,26){}, 
      IDAppointment = 3, IDUser = 3, DurationInHours = 3 
     }, 
     new Note() { 
      AppointmentDate = new DateTime(2013,7,25){}, 
      IDAppointment = 3, IDUser = 3, DurationInHours = 4 
     }, 
     new Note() { 
      AppointmentDate = new DateTime(2013,7,24){}, 
      IDAppointment = 3, IDUser = 3, DurationInHours = 5 
     } 
    } 
); 

var results = from n in notes 
       group n by new {n.IDUser, n.IDAppointment, n.AppointmentDate} 
       into g 
       where g.Key.AppointmentDate > lastMonth && 
        g.Key.IDUser == selectedUserId 
       select new { 
        g.Key.IDAppointment, 
        g.Key.IDUser, 
        TotalHours = g.Sum(n => n.DurationInHours) 
       }; 

需要得到一個明確的名稱（即TotalHours），或者你錯誤CS0746總和屬性：無效的匿名類型成員聲明。匿名類型成員必須聲明爲成員分配，簡單名稱或成員訪問權限。