Linq group by + where for each group - linq

Question

I want to write a linq expression that will return the ID that does not contain a particular value. For example, I want to return all distinct IDs that do not have Value = 30.
ID, Value
1, 10
1, 20
1, 30
2, 10
2, 20
3, 10
3, 20
The result should be 2 and 3 since non of these have a Value with 30.
Is this possible to do with a single expression?
Thanks

Answer 1

Sure, this will do it:
var query = from i in list
group i by i.GroupId into g
where g.Any(p => p.ItemId == 30) == false
select g.Key;
foreach(var result in query) { Console.WriteLine(result); }
This outputs:
2
3
Here I have used, as an example:
class Product {
public int GroupId { get; set; }
public int ItemId { get; set; }
}
and
var list = new List<Product>() {
new Product() {GroupId = 1, ItemId = 10},
new Product() {GroupId = 1, ItemId = 20},
new Product() {GroupId = 1, ItemId = 30},
new Product() {GroupId = 2, ItemId = 10},
new Product() {GroupId = 2, ItemId = 20},
new Product() {GroupId = 3, ItemId = 10},
new Product() {GroupId = 3, ItemId = 20},
};

Answer 2

I don't have Linq, but here is the SQL Server SQL to do what you want:
DECLARE #YourTable table (ID int, value int)
insert into #YourTable VALUES (1, 10)
insert into #YourTable VALUES (1, 20)
insert into #YourTable VALUES (1, 30)
insert into #YourTable VALUES (2, 10)
insert into #YourTable VALUES (2, 20)
insert into #YourTable VALUES (3, 10)
insert into #YourTable VALUES (3, 20)
SELECT DISTINCT ID
FROM #YourTable y1
WHERE NOT EXISTS (SELECT Value
FROM #YourTable y2
WHERE y1.ID=y2.id and y2.value=30)
OUTPUT:
ID
-----------
2
3
(2 row(s) affected)