在LINQ中分组,总和

Question

假设我有下表:

user type amount
2    a    10
2    b    20
2    c    40
3    a    15
3    b    20
3    c    45

我想用(c - (a + b))用户和类型替换(c)金额,我怎么能这样做？谢谢

Answer 1

这是一个方法：

更新（现在使用Sum）：

from item in table
group item by item.user into g
let a = (from i in g where i.type == "a" select i.amount).Sum()
let b = (from i in g where i.type == "b" select i.amount).Sum()
let c = (from i in g where i.type == "c" select i.amount).Sum()
select c - (a + b);