Question

我有一个项目表,包含一个类别领域。这是科索沃联邦统计局。我想把我的项目按类别分类,并归还项目和类别。姓名。

我知道,我可以在C#中这样做:

var ItemsByCat = 
    from i in Items
    group i by i.CategoryId into g
    select g

foreach(var n in ItemsByCat)
{
    blah, blah
}

我的问题是——是否有办法实现分组的部分要素价值,而不必通过 lo子来消化? 类似:

from i in Items
group i by i.CategoryId into g
select new {
    CategoryID = g.Key,
    CategoryName = ???,
    Items = ???
}

非常感谢

BK

Answer 1

我认为,这是你回顾的:

from i in Items
group i by i.CategoryId into g
select new 
{
    CategoryID = g.Key,
    CategoryName = g.First().Category.Name,
    Items = g
}

EDIT:我希望从评论中回答你的问题。

g is a collection of Items grouped by their CategoryId. Items in the select can be a projection including whatever subset of Item properties you require. Example:

from i in Items
group i by i.CategoryId into g
select new 
{
    CategoryID = g.Key,
    CategoryName = g.First().Category.Name,
    Items = g.Select(a => new{a.ItemID, a.ItemName})
}

Answer 2

加入类别表有何意义?

from i in Items
join c in Categories on i.CategoryId equals c.Id
group i by i.CategoryId into g
select new {
    CategoryID = g.Key,
    CategoryName = c.Name,
    Items = i
}

Answer 3

应为:

given you have the relationship setup properly.

The items should be the values of group by, not sure why you d need to do it again.

Answer 4

Assuming you have a collection of Categories in a variable categories it would look like this:

var ItemsByCategory = 
  from i in items
  join c in categories on i.CategoryId equals c.Id
  group i by i.CategoryId into g
  select new {
    CategoryId=g.Key,
    CategoryName=c.Name,
    Items=g.Items
}

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