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("ID") equals dataRows2.Field ("ID") select dtResult.LoadDataRow(new object[] { dataRows1.Field ("ID"), dataRows1.Field ("name"), dataRows2.Field ("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!
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