如何更新linq查詢結果

Question

我將用示例解釋我的問題。

可以說我有linq查詢結果。

var result1=from c in client 
    select new my_type 
    { 
     ... 
      stockDesctiption=?? 

    }; 

我們會說Client已提出所謂stockId。這與dammadgeStockHistory表中的stockId相同。這些表沒有連接任何外鍵約束。

如果我需要得到dammadgeStockHistory.stockDescrption爲每個客戶端如何做到這一點。

Answer 1

加入表按這個領域（不需要外鍵約束）：

var result1 = from c in client 
       join dsh in dammadgeStockHistory 
        on c.stockId equal dsh.stockId 
       select new my_type 
       { 
       stockId = c.stockId, 
       // ...     
       stockDesctiption = dsh.stockDescrption 
       }; 

更新，如果你想要做的 '左連接'：

var result1 = from c in client 
       join dsh in dammadgeStockHistory 
        on c.stockId equal dsh.stockId into g 
       from cdsh in g.DefaultIfEmpty() 
       select new my_type 
       { 
       stockId = c.stockId, 
       // ...     
       stockDesctiption = cdsh == null ? null : dsh.stockDescrption 
       };