Many to many - get appropriate records from table - EF LINQ - entity-framework

Question

I have two tables with relationship many-to-many. Let's say A and B tables.
I also have List<List<int>> TagIdList with ids of B table's elements.
How can I find every elements from table A, who have all TagIdList[i] elements? I need just ids from table A, so it doesn't have to be all TASKS rows from table.
Example:
A: TASKS:
id: 1,2,3,4,5,6
B: TAGS:
id: 1,2,3,4
A-B links:
1-2; 1-3; 2-1; 2-2; 5-3; 5-4; 6-1; 6-6;
List<List<int>> TagIdList //(ids from TAGS)
TagIdList[0]= {2,3}
TagIdList[1]= {1}
TagIdList[2]= {2,6}
Result: (ids from TASKS)
i=0; -> 1
i=1; -> 2,6
i=2; -> null
I've tried:
List<int> tags = model.TagIdList[i].IdList; //I've got it from my View
List<TASKS> tasks = myEntity.TASKS.Where(t => t.TAGS == tags).ToList();
And I can't get tasks, because there was an error: Unable to create a constant value of type. Only primitive types are supported in this context.
Any ideas?

Answer 1

Your problem is here: myEntity.TASKS.Where(t => t.TAGS == tags)
If i understand the question correct you need something like this:
A compare method for two lists of int (Taken from here)
public static bool ScrambledEquals<T>(IEnumerable<T> list1, IEnumerable<T> list2) {
var cnt = new Dictionary<T, int>();
foreach (T s in list1) {
if (cnt.ContainsKey(s)) {
cnt[s]++;
} else {
cnt.Add(s, 1);
}
}
foreach (T s in list2) {
if (cnt.ContainsKey(s)) {
cnt[s]--;
} else {
return false;
}
}
return cnt.Values.All(c => c == 0);
}
Than use this method inside linq expression:
myEntity.TASKS.AsEnumerable().Where(t => ScrambledEquals<int>(t.TAGS.Select(tag=>tag.id).ToList(),tags))

Answer 2

I found solution. It's maybe not ideal, but works.
List<int> tags = model.TagIdList[i].IdList;
List<List<int>> whole_list = new List<List<int>>();
foreach (var t in tags) //I'm looking for every tasks' ids in every given tag
{
var temp = myEntity.TAGS.Find(t).TASKS.Select(task => task.Id).ToList();
whole_list.Add(temp);
}
//now I want first list from whole_list to compare with the other lists
List<int> collection = whole_list[0]; //collection it's tasks
whole_list.Remove(collection);
//I'm taking a part which is common to all lists from whole_list
foreach (List<int> k in whole_list)
{
var temp = collection.Intersect(k);
collection = temp.ToList();
}
//the collection is now what I wanted for TagIdList[i] - every task which has every tags from TagIdList[i].IdList