如何在LINQ中做GroupBy多列
SQL中类似的代码:
SELECT * FROM <TableName> GROUP BY <Column1>,<Column2>
如何将其转换为LINQ:
QuantityBreakdown
(
MaterialID int,
ProductID int,
Quantity float
)
INSERT INTO @QuantityBreakdown (MaterialID, ProductID, Quantity)
SELECT MaterialID, ProductID, SUM(Quantity)
FROM @Transactions
GROUP BY MaterialID, ProductID
当前回答
虽然这个问题问的是按类属性分组，但如果你想对ADO对象(如DataTable)按多列分组，你必须将你的“新”项分配给变量:
EnumerableRowCollection<DataRow> ClientProfiles = CurrentProfiles.AsEnumerable()
.Where(x => CheckProfileTypes.Contains(x.Field<object>(ProfileTypeField).ToString()));
// do other stuff, then check for dups...
var Dups = ClientProfiles.AsParallel()
.GroupBy(x => new { InterfaceID = x.Field<object>(InterfaceField).ToString(), ProfileType = x.Field<object>(ProfileTypeField).ToString() })
.Where(z => z.Count() > 1)
.Select(z => z);
其他回答
.GroupBy(x => (x.MaterialID, x. producd))
需要注意的一点是，您需要为Lambda表达式发送一个对象，而不能为类使用实例。
例子:
public class Key
{
public string Prop1 { get; set; }
public string Prop2 { get; set; }
}
这将进行编译，但每个循环将生成一个键。
var groupedCycles = cycles.GroupBy(x => new Key
{
Prop1 = x.Column1,
Prop2 = x.Column2
})
如果你不想命名键属性，然后检索它们，你可以这样做。这将正确地GroupBy并为您提供关键属性。
var groupedCycles = cycles.GroupBy(x => new
{
Prop1 = x.Column1,
Prop2= x.Column2
})
foreach (var groupedCycle in groupedCycles)
{
var key = new Key();
key.Prop1 = groupedCycle.Key.Prop1;
key.Prop2 = groupedCycle.Key.Prop2;
}
group x by new {x. col, x. col}
虽然这个问题问的是按类属性分组，但如果你想对ADO对象(如DataTable)按多列分组，你必须将你的“新”项分配给变量:
EnumerableRowCollection<DataRow> ClientProfiles = CurrentProfiles.AsEnumerable()
.Where(x => CheckProfileTypes.Contains(x.Field<object>(ProfileTypeField).ToString()));
// do other stuff, then check for dups...
var Dups = ClientProfiles.AsParallel()
.GroupBy(x => new { InterfaceID = x.Field<object>(InterfaceField).ToString(), ProfileType = x.Field<object>(ProfileTypeField).ToString() })
.Where(z => z.Count() > 1)
.Select(z => z);
从c# 7开始，你也可以使用值元组:
group x by (x.Column1, x.Column2)
or
.GroupBy(x => (x.Column1, x.Column2))
