LINQ加入两个DataTables

Question

嗨,我在使用LINQ加入两个DataTable时遇到问题.表有这样的列:

table1        table2
ID, name       ID, stock
1, item1       1, 100
2, item2       3, 50
3, item3

我用linq这样加入:

DataTable dtResult = new DataTable();
dtResult.Columns.Add("ID", typeof(string));
dtResult.Columns.Add("name", typeof(string));
dtResult.Columns.Add("stock", typeof(int));

var result = from dataRows1 in table1.AsEnumerable()
             join dataRows2 in table2.AsEnumerable()
             on dataRows1.Field<string>("ID") equals dataRows2.Field<string>("ID")

             select dtResult.LoadDataRow(new object[]
             {
                dataRows1.Field<string>("ID"),
                dataRows1.Field<string>("name"),
                dataRows2.Field<int>("stock"),
              }, false);
result.CopyToDataTable();

问题是,结果只显示表2中的ID.

dtResult
ID, name, stock
1, item1, 100
3, item3, 50

我还要展示丢失的物品.这是想要的结果:

dtResult
ID, name, stock
1, item1, 100
2, item2, 0  //Prefer if it is "0", otherwise can be left "null"
3, item3, 50

我相信我应该做左外连接,但我对linq没有足够的了解.帮助赞赏.谢谢!

Answer 1

如果table2中不存在行,这将允许您默认为0:

var result = from dataRows1 in table1.AsEnumerable()
             join dataRows2 in table2.AsEnumerable()
             on dataRows1.Field<string>("ID") equals dataRows2.Field<string>("ID") into lj
             from r in lj.DefaultIfEmpty()
             select dtResult.LoadDataRow(new object[]
             {
                dataRows1.Field<string>("ID"),
                dataRows1.Field<string>("name"),
                r == null ? 0 : r.Field<int>("stock")
              }, false);

MSDN 来源