LINQ GROUP BY和SUM

Question

可能重复：
Get sum of two columns in one LINQ query

我需要知道如何写一个LINQ查询，这将使我同样的结果，因为这SQL查询 ：

select sum(col1) as [col1] , sum(col2) as [col2] , sum(col1)/sum(col2) as [col3], col4 as [col4] 
from some_table 
group by col4 

Answer 1

完整的道具去Steven为此答案：https://stackoverflow.com/a/2432348/211627

from row in some_table 
group row by row.col4 into g 
select new 
{ 
    col1 = g.Sum(x => x.col1), 
    col2 = g.Sum(x => x.col2), 
    col3 = g.Sum(x => x.col1)/g.Sum(x => x.col2), 
    col4 = g.Key 
}; 

Answer 2

或者和λ，我假设some_table是一个实体或库..等

some_table.GroupBy(row => row.col4).Select(row => new 
{ 
    col1 = row.Sum(x => x.col1), 
    col2 = row.Sum(x => x.col2), 
    col3 = row.Sum(x => x.col1)/row.Sum(x => x.col2), 
    col4 = row.Key 
}); 

Answer 3

这是假设你的表是某种实体。这会将其放入一个Anonymous Type，但也可用于创建您自己的类型的对象。

myInitialCollection.GroupBy(x => x.Col4).Select(x => 
    new { 
      col1 = x.Sum(y => y.Col1), 
      col2 = x.Sum(y => y.Col2), 
      col3 = (x.Sum(y => y.col1)/x.Sum(y => y.col2)), 
      col4 = x.Key 
    });