使用 select 语句对多级对象进行 Linq Group
我有 3 个数据集对象，它们使用实体集对象相互嵌套。我正在选择这样的数据
var newList = from s in MainTable
from a in s.SubTable1 where a.ColumnX = "value"
from b in a.Detail where b.Name = "searchValue"
select new {
ID = s.ID,
Company = a.CompanyName,
Name = b.Name,
Date = s.DueDate
Colour = b.Colour,
Town = a.Town
};
，这工作正常，但问题是每个名称值的详细信息对象列表/表中都有许多记录，因此我会得到大量重复行，因此我只想为每个名称显示一条记录b. 姓名。我尝试将其放在
group s by b.Name into g
选择之前，但这似乎会停止选择，使我能够选择我想要的列（实际上还有更多列）。在这种情况下如何使用 group 命令，同时仍保持输出行为“平面”格式？
I've got 3 dataset objects that are nested with each other using entity set objects. I am selecting the data like this
var newList = from s in MainTable
from a in s.SubTable1 where a.ColumnX = "value"
from b in a.Detail where b.Name = "searchValue"
select new {
ID = s.ID,
Company = a.CompanyName,
Name = b.Name,
Date = s.DueDate
Colour = b.Colour,
Town = a.Town
};
and this works fine, but the trouble is there are many records in the Detail object-list/table for each Name value so I get a load of duplicate rows and thus I only want to display one record per b.Name. I have tried putting
group s by b.Name into g
before the select, but then this seems to stop the select enabling me to select the columns I want (there are more, in practice). How do I use the group command in this circumstance while still keeping the output rows in a "flat" format?
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附加评论作为结束问题的答案：-
当然，如果对结果进行分组，则无法选择子项的一列，那是因为可能有多个子项，并且您必须指定一个聚合列，例如 sum,max etx –
Appending comment as answer to close question:-
Of course that if you group your results, you cant get select a column of a child, thats because there may be more than one childs and you have to specify an aggregate column for example the sum,max etx –