Question

我需要查询几个数据集。使用linq，我最终得到这样的代码..

var query =
     from table1 in table_1.AsEnumerable()
     join table2 in table_2.AsEnumerable()
on table1.Field<string>("Value1") equals
   table2.Field<string>("value2") into join1
from joinData in join1.AsEnumerable()
join table1_1 in table_1.AsEnumerable()
on joinData.Field<string>("Value3") equals
   table1_1.Field<string>("Value1")
into join2
from joinData2 in join2.AsEnumerable()
where joinData2.Field<string>("Value4") == "1" ||
      joinData2.Field<string>("Value4") == "2" ||
      joinData2.Field<string>("Value4") == "3" ||
      joinData2.Field<string>("Value4") == "4" ||
      joinData2.Field<string>("Value4") == "5" ||
      joinData2.Field<string>("Value4") == "6" ||
      joinData2.Field<string>("Value4") == "7" ||
      joinData2.Field<string>("Value4") == "8"
select new
{
    Value1 = data1.Field<string>("Value1"),
    Value2 = data1.Field<string>("Value2"),
    Value3 = data1.Field<string>("Value3"),
    Value4 = data1.Field<string>("Value4"),
    Value5 = data1.Field<string>("Value5"),
    Value6 = data1.Field<string>("Value6"),
    Value7 = data1.Field<string>("Value7"),
    Value8 = data1.Field<string>("Value8"),
    Value9 = data1.Field<string>("Value9"),
    Value10 = data1.Field<string>("Value10"),
    Value11 = data1.Field<string>("Value11"),
    Value12 = data1.Field<string>("Value12"),

    etc...
};

必须有一种更简单的方法来做到这一点。有没有办法只使用SQL语句查询数据集？

Answer 1

您可以简化WHERE部分：

where joinData2.Field<string>("Value4") == "1" ||
      joinData2.Field<string>("Value4") == "2" ||
      joinData2.Field<string>("Value4") == "3" ||


where List<string>{ "1", "2", "3", ... }
      .Contains( joinData2.Field<string>("Value4"))

也许你可以将SELECT部分重构为构造函数（非匿名类型）。

但不，你不能将SQL应用于数据集（超出你已经在使用LINQ做的事情）。

考虑使用像Entity框架这样的ORM，这会让生活变得更轻松。

使用LINQ对数据集进行复杂查询

1 个答案: