LINQ在哪里存在GROUP BY

Question

如何在LINQ中将其转换？

SELECT B.SENDER, B.SENDNUMBER, B.SMSTIME, B.SMSTEXT 
FROM MESSAGES B 
WHERE EXISTS (SELECT A.SENDER 
     FROM MESSAGES A 
    WHERE A.SENDER = B.SENDER 
    GROUP BY A.SENDER 
    HAVING B.SMSTIME = MAX(A.SMSTIME)) 
GROUP BY B.SENDER, B.SENDNUMBER, B.SMSTIME, B.SMSTEXT ; 

感谢很多:)

编辑！

解决了与：

var Condition = "order by SMSTime desc";  

    IEnumerable<ClassMessaggio> messaggi = Database.Select<ClassMessaggio>(Condition);; // Load all but sorted 

    ElencoConversazioni = messaggi.GroupBy(m => new { m.Number }) 
       .Select(g => g.OrderByDescending(m => m.SMSTime).First()).ToObservableCollection(); 

Answer 1

尝试

db.Messages.Where(b => b.SmsTime == Messages.Where(a => a.Sender == b.Sender) 
              .Max(a => a.SmsTime)) 

或者

db.Messsages.GroupBy(m => new { m.Sender, m.SendNumber }) 
      .Select(g => g.OrderByDescending(m => m.SmsTime).First()) 

哪里db是你的DataContext。

Answer 2

以示与“每一个接触的最后一条消息”沿会话列表，你可以尝试这样的：

// a query to find the last Sms time per sender 
var lastSmsQuery = from m in db.messages 
       group m by m.Sender into grouping 
       select new 
       { 
        Sender = grouping.Key, 
        LastSmsTime = grouping.Max(x => x.SmsTime) 
       }; 

// a query to find the messages linked to the last Sms per sender 
var lastMessageQuery = from m in db.messages 
         join l in lastSmsQuery on new { m.Sender, m.SmsTime } equals new { l.Sender, l.LastSmsTime } 
         select m; 

使用的2-查询方法类似于从今天早些时候这个问题 - Convert SQL Sub Query to In to Linq Lambda