C# LINQ to Datatable Group by 并返回所有列
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LINQ to Datatable Group by and return all columns
提问by vicky
I have a Datatable
我有一个数据表
ID Age Last name First Name Sex class Father_Name Mother_Name Marks
1 20 A B M 1 A B 50
1 20 A B M 1 A B 50
1 20 A B M 1 A B 100
2 15 F G F 2 H J 40
2 15 F G F 2 H J 50
& I want following results after applying Linq Group by
＆我希望在应用 Linq Group 后获得以下结果
1 20 A B M 1 A B 200
2 15 F G F 2 H J 90
I am able to get the sum but i am not able to get the other columns in LINQ group by
我能够得到总和，但我无法得到 LINQ 组中的其他列
Can anyone help on this
谁能帮忙解决这个问题
var drResults = from r1 in dtResults.AsEnumerable()
group r1 by new
{
MarksSum= r1.Field<int>("Marks"),
}
into g
select new
{
Total = g.Sum(r1=>r1.Field<int>("Marks"))
};
采纳答案by John Woo
var _result = from r1 in dtResults.AsEnumerable()
group r1 by new
{
ID = r1.Field<int>("ID"),
Age = r1.Field<int>("Age"),
LastName = r1.Field<int>("LastName"),
FirstName = r1.Field<int>("FirstName"),
Sex = r1.Field<int>("Sex"),
Class = r1.Field<int>("class"),
Father_Name = r1.Field<int>("Father_Name"),
Mother_Name = r1.Field<int>("Mother_Name")
} into g
select new
{
ID = g.Key.ID,
Age = g.Key.Age,
LastName = g.Key.LastName,
FirstName = g.Key.FirstName,
Sex = g.Key.Sex,
Class = g.Key.Class,
Father_Name = g.Key.Father_Name,
Mother_Name = g.Key.Mother_Name,
TotalMark = g.Sum(x => x.Field<int>("Marks"))
};
回答by Tim Schmelter
You want to group by the Id?! Then you can use Sumthe Markson the group:
你想分组Id吗？！然后你可以使用Sum在Marks该组：
var result = from r in dtResults.AsEnumerable()
group r by r.Field<int>("ID") into IdGroup
let row = IdGroup.First()
select new
{
ID = IdGroup.Key,
Age = row.Field<int>("Age"),
LastName = row.Field<string>("Last_Name"),
FirstName = row.Field<string>("First_Name"),
MotherName = row.Field<string>("Mother_Name"),
FatherName = row.Field<string>("Father_Name"),
Marks = IdGroup.Sum(r => r.Field<int>("Marks"))
};
Update
更新
Hey Tim, if all rows have different values then what should i do? e.g LastName is different and ID is same. I have some data which is corrupt or you can say redundant in that case i am asking.
嘿蒂姆，如果所有行都有不同的值，那么我该怎么办？例如，姓氏不同，ID 相同。我有一些已损坏的数据，或者在这种情况下您可以说是多余的。
It's out of the scope of this question to show how you can "repair" your DataTable. But if you instead want to list all rows even when they have the same ID, but witht he correct summed Markper Id-Group, you can use this query:
展示如何“修复”您的DataTable. 但是，如果您想列出所有行，即使它们具有相同的 ID，但Mark每个 Id-Group 的总和正确，您可以使用以下查询：
var result = from r in dtResults.AsEnumerable()
group r by r.Field<int>("ID") into IdGroup
let IdTotalMarks = IdGroup.Sum(r => r.Field<int>("Marks"))
from row in IdGroup
select new
{
ID = IdGroup.Key,
Age = row.Field<int>("Age"),
LastName = row.Field<string>("Last Name"),
FirstName = row.Field<string>("First Name"),
MotherName = row.Field<string>("Mother Name"),
FatherName = row.Field<string>("Father_Name"),
Marks = IdTotalMarks
};
回答by Oliver
JW's answer with Lambda syntax (I have also renamed the field "class" as this won't compile):
JW 对 Lambda 语法的回答（我还重命名了字段“class”，因为这不会编译）：
var _result = dtResults
.AsEnumerable()
.GroupBy(r1 => new
{
ID = r1.Field<int>("ID"),
Age = r1.Field<int>("Age"),
LastName = r1.Field<string>("LastName"),
FirstName = r1.Field<string>("FirstName"),
Sex = r1.Field<int>("Sex"),
Class = r1.Field<int>("class"),
Father_Name = r1.Field<string>("Father_Name"),
Mother_Name = r1.Field<string>("Mother_Name")
}).Select(g => new
{
ID = g.Key.ID,
Age = g.Key.Age,
LastName = g.Key.LastName,
FirstName = g.Key.FirstName,
Sex = g.Key.Sex,
Class = g.Key.Class,
Father_Name = g.Key.Father_Name,
Mother_Name = g.Key.Mother_Name,
TotalMark = g.Sum(x => x.Field<int>("Marks"))
});
