C＃lambda內部連接最大

Question

我創建了這個sql查詢，但我很難將其轉換爲linq lambda。我對linq相當陌生。

Select t1.* Fom msgs as t1 
Inner join(
    Select fromUser, MAX(ts) as mts 
    From msgs 
    Where toUser='aUserName' AND isDeleted='0' 
    Group By fromUser 
)t2 On (t2.fromUser=t1.fromUser and t1.ts = t2.mts) Order By ts desc; 

Answer 1

你可以做到同樣的事情OrderByDescending（LINQ擴展）和GroupBy。

var messages = msg.ToList(); 
var results = messages.Where(x=> x.toUser = "aUserName" AND isDeleted="0") 
    .GroupBy(x=>x.fromUser) 
    .Select(x=> 
    { 
     var maxitem = x.OrderByDescending(y=>y.ts).First(); 
     return new 
     { 
       fromUser = maxItem.fromUser, 
       ts = maxitem.ts, 
       ... // remaining properties. 
     } 
    }) 
    .ToList();