LINQ query operator for log table - linq

Question

I am trying to find the corerct LINQ to SQL query operator and predicate combo that can operate on an audit table.
Imagine a table called Setting that has three columns : rowID, DefID, and Value.
I want to be able to check that every DefID ( in this case all definition 1 through 3 ) has at least one row which has a value set to true.
the LINQ expression should return a bool true or false. For example,
RowID DefID Value
1 1 true
2 2 false
3 3 true
LINQ returns false because DefID = 2 does not have any value = true
RowID DefID Value
1 1 true
2 2 false
3 2 true
returns false because defid 3 is missing
RowID DefID Value
1 1 true
2 1 false
3 2 true
4 3 true
returns true because ALL definitions have at least one value = true

Answer 1

Here is an example using extension methods:
int[] ids = new int[] { 1, 2, 3 };
bool allFound = Settings.Where( s => s.Value && ids.Contains( s.DefID ) )
.Select( s => s.DefID )
.Distinct()
.Count() == ids.Length;

Answer 2

I've never used linq to sql, but the linq to objects would look something like this:
defIds.All(d => d.rows.Any( row => row.Value == true ) )
To do it in raw SQL, I don't think it's possible in one query. You could do something like this though:
select id from DefIds
join rows on row.DefId = DefIds.ID
where row.Value = true
That would give you a list of defId's which have true values. In code you could then do something like
DefIds.Select(d => d.id).ToArray() == (results from select).ToArray()

Answer 3

Well, there are a lot of valid ways to do this. One simple way is:
int[] DefIDs = new int[] {1, 2, 3};
bool bHasValidDefs =
(
from set in myDataBase.settings
where
set.Value == true
&& DefIDs.Contains(set.DefID)
select set.DefID
).Distinct().Count() == DefIDs.Count();
This gets the number of unique DefIDs that are in your valid list and also have at least one "value == true" row. It then makes sure that the number of these valid DefIDs is equal to the expected value that you define above.

Answer 4

If you are ok with having a ValidSettings or SettingsMaster table, you could:
bool allFound = myContext.SettingsMaster.All(m=> m.Settings.Any(s=>s.Value));
For the current tables version, I would
int[] allIds = new int[] {1, 2, 3};
var validIds = (
from s in myContext.Settings
where s.Value
select s.DefId
)
.Distinct().ToList();
bool allFound = allIds.All(id => validIds.Contains(id));