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
您还可以使用Tuple<>作为强类型分组。
from grouping in list.GroupBy(x => new Tuple<string,string,string>(x.Person.LastName,x.Person.FirstName,x.Person.MiddleName))
select new SummaryItem
{
LastName = grouping.Key.Item1,
FirstName = grouping.Key.Item2,
MiddleName = grouping.Key.Item3,
DayCount = grouping.Count(),
AmountBilled = grouping.Sum(x => x.Rate),
}
其他回答
程序样例:
.GroupBy(x => new { x.Column1, x.Column2 })
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))
.GroupBy(x => x.Column1 + " " + x.Column2)
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);
对于多列组，试试这个…
GroupBy(x=> new { x.Column1, x.Column2 }, (key, group) => new
{
Key1 = key.Column1,
Key2 = key.Column2,
Result = group.ToList()
});
同样的方法，您可以添加Column3, Column4等。
