LEFT OUTER JOIN 2 datatables

Question

我想了解如何查詢，最好是LINQ，2個數據表。 我願做一個LEFT OUTER JOIN他們

Datatable1與山口的：[ID] [可口可樂]
DataTable2與山口的：[ID] [COLB] [COLC] ...

展望加入該ID。

有人可以告訴我一個例子，所以我可以將它應用到我有的數據表中嗎？謝謝你在前進

Answer 1

這編譯並做你會是什麼根據給定的結果預期：

// create the default row to be used when no value found 
var defaultRow = DataTable2.NewRow(); 
defaultRow[0] = 0; 
defaultRow[1] = String.Empty; 

// the query 
var result = from x in DataTable1.AsEnumerable() 
    join y in DataTable2.AsEnumerable() on (string)x["ID"] equals (string)y["ID"] 
      into DataGroup 
    from row in DataGroup.DefaultIfEmpty<DataRow>(defaultRow) 
    select new {a = x["ColA"], b = (string)row["ColB"]}; 

Answer 2

爲了得到一個內部聯接嘗試這種

from x in Datatable1 
join y in Datatable2 on x.ID equals y.ID 
select new {x.colA, y.ColB, y.ColC } 

Answer 3

要獲得LEFT OUTER Join

，你應該嘗試使用@Joanna鏈接。

from x in DataTable1 
join y in DataTable2 on x.ID equals y.ID into DataGroup 
from item in DataGroup.DefaultIfEmpty(new y.ColB = String.Empty , y.ColC = String.Empty}) 
select new {x.ColA, item.ColB , item.ColC} 

UPDATE

鑑於你提供你應該尋找LINQ的數據集文章

這裏是代碼片段

DataTable DataTable1 = new DataTable(); 
DataTable DataTable2 = new DataTable(); 

DataTable1.Columns.Add("ID"); 
DataTable1.Columns.Add("ColA"); 
DataTable1.Rows.Add(1, "A"); 
DataTable1.Rows.Add(2, "B");  

DataTable2.Columns.Add("ID"); 
DataTable2.Columns.Add("ColB"); 
DataTable2.Rows.Add(1, "B"); 

var result = from x in DataTable1.AsEnumerable() 
      join y in DataTable2.AsEnumerable() on x["ID"] equals y["ID"] into DataGroup       
      from item in DataGroup.DefaultIfEmpty() 
      select new { 
          ID = x["ID"], 
          ColA = x["ColA"], 
          ColB = item == null ? string.Empty : item["ColB"] 
         }; 
foreach (var s in result) 
    Console.WriteLine("{0}", s);