Ef6點符號;與條件colums加入喜歡，不等於

Question

我想加入基於ID列兩個表上Table2是在像列IDTable1

me.dbSet.Join(me.context.Table2, p => p.ID, e => e.ID, 
(p, e) => new { p, e }).Where(z => z.e.ID== uid) 

的SQL輸出：

SELECT 
    1 AS [C1] 
    FROM [NG].[T1] AS [Extent1] 
    INNER JOIN [NG].[T2] AS [Extent2] ON [Extent1].[ID] = [Extent2].[ID] 
    WHERE [Extent2].[ID] = 'f520f7b3-215d-4dfe-9787-1eb6864fb335' 

我試圖用linq寫的sql：

SELECT 
    1 AS [C1] 
    FROM [NG].[T1] AS [Extent1] 
    INNER JOIN [NG].[T2] AS [Extent2] ON [Extent1].[ID] Like [Extent2].[ID] + '%' 
    WHERE [Extent2].[ID] = 'f520f7b3-215d-4dfe-9787-1eb6864fb335' 

Answer 1

您可以與where子句中交叉聯接和StartsWith做到這一點：

var data = from t1 in Table1 
      from t2 in Table2 
      where t1.Id.StartsWith(t2.Id) 
      && t2.Id == uid 
      select new { t1, t2 }; 

它不會給予同樣的SQL，只要你想，但輸出是一樣的。只有

未經檢驗的，但使用lambda擴展方法，這應該工作：

var data = me.dbSet 
    .Join(
     me.context.Table2, 
     p => true, 
     e => true, 
     (p, e) => new { p, e }) 
    .Where(z => z.e.ID == uid && z.p.Id.StartsWith(z.e.Id)); 

另一個潛在的選擇，如果你知道ID的長度是不變的（它看起來像一個GUID，所以你也許可以依靠它長爲36個字符：

var data = me.dbSet 
    .Join(
     me.context.Table2, 
     p => p.Id.Substring(0, 36), 
     e => e.Id, 
     (p, e) => new { p, e }) 
    .Where(z => z.e.ID == uid);