在差异列上加入2个数据表

Question

我有2个DataTable。我想使用LINQ在差异列上加入2个数据表。怎么做？

表A：

+--------+-------+-------+
| ACol1  | ACol2 | ACol3 |
+--------+-------+-------+
|      1 | tbA12 | tbA13 |
|      2 | tbA22 | tbA23 |
|      3 | tbA32 | tbA33 |
|      4 | tbA42 | tbA43 |
|      5 | tbA52 | tbA53 |
+--------+-------+-------+

表B：

+-------+-------+-------+
| BCol1 | BCol2 | BCol3 |
+-------+-------+-------+
| 1     | XX    | tbB13 |
| XX    | 1     | tbB23 |
| XX    | 2     | tbB33 |
| 4     | XX    | tbB43 |
+-------+-------+-------+

SQL查询：

SELECT a.*, b.BCol3
FROM tableA a
JOIN tableB b ON a.ACol1=b.BCol1 OR a.ACol1=b.BCol2

预期结果：

+--------+-------+-------+-------+
| ACol1  | ACol2 | ACol3 | BCol3 |
+--------+-------+-------+-------+
|      1 | tbA12 | tbA13 | tbB13 |
|      1 | tbA12 | tbA13 | tbB23 |
|      2 | tbA22 | tbA23 | tbB33 |
|      4 | tbA42 | tbA43 | tbB43 |
+--------+-------+-------+-------+

目前我的LINQ查询如下：

var query1= from rowA in tableA.AsEnumerable()
            join rowB in tableB.AsEnumerable()
            on rowA["ACol1"].ToString() equals rowB["BCol1"].ToString()
            select new
            {
                rowA["ACol1"],
                rowA["ACol2"],
                rowA["ACol3"],
                rowB["BCol3"]
            };

var query2= from rowA in tableA.AsEnumerable()
            join rowB in tableB.AsEnumerable()
            on rowA["ACol1"].ToString() equals rowB["BCol2"].ToString()
            {
                rowA["ACol1"],
                rowA["ACol2"],
                rowA["ACol3"],
                rowB["BCol3"]
            };

var result=query1.Union(query2);

更好的想法如何解决这个问题？

Answer 1

LINQ对具有非平凡条件的JOIN的支持非常有限。您可以进行交叉连接+将条件移动到where子句。

var query1= from rowA in tableA.AsEnumerable()
            from rowB in tableB.AsEnumerable()
            where rowA["ACol1"].ToString() == rowB["BCol1"].ToString()
            || rowA["ACol1"].ToString() == rowB["BCol2"].ToString()
            select new
            {
                rowA["ACol1"],
                rowA["ACol2"],
                rowA["ACol3"],
                rowB["BCol3"]
            };

Answer 2

试试这个： -

var result = from a in tableA.AsEnumerable()
             from b in tableB.AsEnumerable()
             where a.Field<string>("ACol1") == b.Field<string>("BCol1")
                || a.Field<string>("ACol1") == b.Field<string>("BCol2")
             select new
                    {
                        a["ACol1"],
                        a["ACol2"],
                        a["ACol3"],
                        b["BCol3"]
                    };

以下是完整的工作Fiddle，您可以在编辑器中复制粘贴并进行测试，因为它不支持DotNetFiddle中的AsEnumerable。