C＃SQL語句轉換為LINQ我如何將此語句轉換為可用的linq

Question

我對此有麻煩，我有3次重復使用的數據表，這些數據表被緩存了，我想寫一個LINQ語句，這樣做可能嗎？

T-SQL版本：

SELECT P.[CID],P.[AID]
 ,B.[AID], B.[Data], B.[Status], B.[Language]
 FROM MY_TABLE_1 P
 JOIN 
  (
   SELECT A.[AID], A.[Data], A.[Status], A.[Language] FROM MY_TABLE_2 A  
   UNION ALL
   SELECT B.[AID], B.[Data], B.[Status], B.[Language] FROM MY_TABLE_3 B
  ) B on P.[AID] = B.[AID]
WHERE B.[Language] = 'EN' OR  B.[Language] = 'ANY' AND B.STATUS = 1 AND B.[Language] = 'EN' OR  B.[Language] = 'ANY' AND B.STATUS = 1

然后我希望它創建以下結果集

結果： | CID | AID | DATA |狀態|語言

Answer 1

嘗試這個：

from p in Context.MyTable1
join b in Contact.MyTable2.Concat(Contact.MyTable3)
  on p.aid equals b.aid
where b.Language == "EN" || b.Language == "ANY"
where b.Status == 1
select new
{
    p.CID,
    p.AID,
    b.Data,
    b.Status,
    b.Language
};

Answer 2

不要這樣

您的兩個選擇

1. 創建一個表示您的Union語句的視圖（表2和表3）
2. 在Table1和AID列上的新視圖之間的DBML上創建關系。
3. 執行SelectMany以獲取所需的返回結果。

或（首選）

• 創建一個接受語言/狀態（假設它們是參數）的存儲過程，並返回此數據集。 這將是最有效的方法。

您正在按照業務邏輯進行數據庫工作！ 使用數據庫以達到預期的目的。

Answer 3

確保引用System.Data.DataSetExtensions，並使用AsEnumerable（）方法對數據集使用LINQ。

            var myTable1 = new [] { 
            new { CID = "123", AID = 345, Data = 32323, Status = 1, Language = "EN"},
            new { CID = "231", AID = 123, Data = 11525, Status = 2, Language = "EN"},
            new { CID = "729", AID = 513, Data = 15121, Status = 1, Language = "ANY"},
            new { CID = "231", AID = 123, Data = 54421, Status = 2, Language = "EN"}}
            .ToDataTable().AsEnumerable();

        var myTable2 = new [] { 
            new { CID = "512", AID = 513, Data = 32323, Status = 1, Language = "ANY"},
            new { CID = "444", AID = 123, Data = 11525, Status = 2, Language = "BLAH"},
            new { CID = "222", AID = 333, Data = 15121, Status = 1, Language = "ANY"},
            new { CID = "111", AID = 345, Data = 54421, Status = 2, Language = "EN"}}
            .ToDataTable().AsEnumerable();

         var myTable3 = new [] { 
            new { CID = "888", AID = 123, Data = 32323, Status = 2, Language = "EN"},
            new { CID = "494", AID = 333, Data = 11525, Status = 1, Language = "FR"},
            new { CID = "202", AID = 513, Data = 15121, Status = 1, Language = "EN"},
            new { CID = "101", AID = 345, Data = 54421, Status = 2, Language = "ANY"}}
            .ToDataTable().AsEnumerable();

         var q = from p in myTable1
                 join b in myTable2.Union(myTable3) on p.Field<int>("AID") equals b.Field<int>("AID")
                 where (b.Field<string>("Language") == "EN" || b.Field<string>("Language") == "ANY") && b.Field<int>("Status") == 1
                 select new
                 {
                     CID = p.Field<string>("CID"),
                     B_AID = p.Field<int>("AID"),
                     P_AID = b.Field<int>("AID"),
                     Data = b.Field<int>("Data"),
                     Status = b.Field<int>("Status"),
                     Language = b.Field<string>("Language")
                 };


         var table = q.ToDataTable();

我使用了一種擴展方法，可以在此處進行測試，如果您在DataTables上執行大量的LINQ，這將非常有用。