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按多列分组

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如何在LINQ中执行GroupBy多列

SQL中与此类似的东西：

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
.net linq group-by aggregate

12 回答

  • 8

    程序样本

    .GroupBy(x => new { x.Column1, x.Column2 })
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  • 1080

    使用匿名类型 .

    例如

    group x by new { x.Column1, x.Column2 }
    回复于
  • 2

    x由新{x.Col，x.Col}组成

    回复于
  • 16

    .GroupBy(x => (x.MaterialID, x.ProductID))

    回复于
  • 5

    需要注意的是，您需要为Lambda表达式发送一个对象，并且不能为类使用实例 .

    例：

    public class Key
{
    public string Prop1 { get; set; }

    public string Prop2 { get; set; }
}

    这将编译但会生成 one key per cycle .

    var groupedCycles = cycles.GroupBy(x => new Key
{ 
  Prop1 = x.Column1, 
  Prop2 = x.Column2 
})

    如果您不想命名关键属性然后检索它们，您可以这样做 . 这将正确 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;
}
    回复于
  • 657

    您还可以使用元组<>进行强类型分组 .

    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),
}
    回复于
  • 127

    从C＃7开始，你也可以使用值元组：

    group x by (x.Column1, x.Column2)

    要么

    .GroupBy(x => (x.Column1, x.Column2))
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  • 0

    虽然这个问题是按类属性询问，但是如果要针对ADO对象（如DataTable）按多个列进行分组，则必须将“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);
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  • 18
    var Results= query.GroupBy(f => new { /* add members here */  });
    回复于
  • 431

    好的，这是：

    var query = (from t in Transactions
             group t by new {t.MaterialID, t.ProductID}
             into grp
                    select new
                    {
                        grp.Key.MaterialID,
                        grp.Key.ProductID,
                        Quantity = grp.Sum(t => t.Quantity)
                    }).ToList();
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  • 2
    .GroupBy(x => x.Column1 + " " + x.Column2)
    回复于
  • 2

    对于按多列分组，请尝试此操作...

    GroupBy(x=> new { x.Column1, x.Column2 }, (key, group) => new 
{ 
  Key1 = key.Column1,
  Key2 = key.Column2,
  Result = group.ToList() 
});

    以同样的方式添加Column3，Column4等 .

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