.NET[C#]LINQ按多列分组(Group By)并计算总和(Sum)

SQL语句：

SELECT * FROM <TableName> GROUP BY <Column1>,<Column2>

QuantityBreakdown

(

    MaterialID int,

    ProductID int,

    Quantity float

)

INSERT INTO @QuantityBreakdown (MaterialID, ProductID, Quantity)

SELECT MaterialID, ProductID, SUM(Quantity)

FROM @Transactions

GROUP BY MaterialID, ProductID

在C#中，如何使用LINQ实现以上SQL语句中的需求呢？方式归纳如下：

方式一

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();

方式二

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),

}

方式三

var Results= query.GroupBy(x => new { x.Column1, x.Column2 });