c# - 分组和计数

Question

我从数据库中检索数据，就像这样

ID - item ID  - State - type  - comment
===
1  - 158      -   0   - 114589- AAAAA    
2  - 158      -   1   - 108965- BBBBB    
3  - 159      -   1   - 100145- CCCCC    
4  - 159      -   0   - 100145- DDDDD    
5  - 159      -   1   - 114589- EEEEE    
6  - 162      -   0   - 100145- FFFFF    
7  - 162      -   1   - 108965- GGGGG

我需要返回结果选择项目 ID，按项目 ID、状态、类型和评论分组的状态计数

如何使用 LINQ 做到这一点？

Answer 1

var grouped = from x in yourList
             group by new {x.itemID, x.type ,x.comment };

var counts = grouped.Select(x=>new {key = x.Key, count = x.Count());

Answer 2

我不确定你的意思，但我认为这就是你想要的：

var result = 
   from d in dataList
   group d by new { d.State, d.Type, d.Comment } in g
   select new { ItemId = g.Key, StateCount = g.Count(m => m.State) } 
   // I don't know what you mean with count the state. 
   // If you mean sum then you can use g.Sum(m => m.State) instead of g.Count(..)

Answer 3

from DataRow row in dataSet
group row by new
{
    ID = (int) row["ID"],
    State = row["State"].ToString(),
    Type = (int)row["type"],
    Comment = row["comment"].ToString()
} into rowGroup
select new
{
    Key = rowGroup.Key,
    Count = rowGroup.Count()
};