LINQ：使用INNER JOIN，Group和SUM

我正在尝试使用LINQ执行以下SQL，而我最接近的是进行交叉连接和求和计算。 我知道必须有一个更好的方法来编写它，所以我转向堆栈团队寻求帮助。

SELECT T1.Column1, T1.Column2, SUM(T3.Column1) AS Amount FROM T1 INNER JOIN T2 ON T1.T1ID = T2.T1ID INNER JOIN T3 ON T2.T3ID = T3.T3ID GROUP BY T1.Column1, T1.Column2 

我一直在尝试的是以下LINQ代码

 var qTotal = from T2 in context.T2 from T3 in context.T3 where T3.T3ID == T3.T3ID group T3 by T2.T1ID into gT2T3 from T1 in context.T1 where gT2T3.Key.Equals(T1.T1ID) select new { T1.Column1,T1.Column2,Amount = gT2T3.Sum(t => t.Column1)}; 

我知道必须有更好的方法来编写它，我只是不知道如何，任何帮助都会很棒！

Answer 1

试试这个：

 var total = from T1 in context.T1 join T2 in context.T2 on T1.T2ID equals T2.T2ID join T3 in context.T3 on T2.T3ID equals T3.T3ID group T3 by new { T1.Column1, T1.Column2 } into g select new { Column1 = T1.Column1, Column2 = T2.Column2, Amount = g.Sum(t3 => t3.Column1) }; 

Answer 2

对我来说（使用4.0），以下工作。

 var total = from T1 in context.T1 join T2 in context.T2 on T1.T2ID equals T2.T2ID join T3 in context.T3 on T2.T3ID equals T3.T3ID group T3 by new { T1.Column1, T1.Column2 } into g select new { Column1 = g.Key.Column1, Column2 = g.Key.Column2, Amount = g.Sum(t3 => t3.Column1) }; 

Answer 3

下面的代码对我有用：

  var credit = (from bm in BulkMessage join sms in SMS on bm.BulkMessageId equals sms.BulkMessageId where bm.ProfileId == pid && bm.IsActive == true group sms by sms.SMSCredit into g select new { SMSCredits = g.Sum(s => s.SMSCredit) }).FirstOrDefault();