左外連接問題

Question

我需要將某些SQL語句轉換爲LINQ。如何將LEFT OUTER JOIN轉換爲等效的LINQ語句？

Answer 1

您需要使用DefaultIfEmpty運算符。下面的代碼應該導致左外連接。

var q = from c in customers 
      join o in orders on c.Key equals o.Key into g 
      from o in g.DefaultIfEmpty() 
      select new {Name = c.Name, OrderNumber = o == null ? "(no orders)" :  o.OrderNumber}; 

感謝：http://www.hookedonlinq.com/OuterJoinSample.ashx