C# Linq select object in List where int in object child List<int> occurs n times

Question

I have a List<TestObj> ListOfTestObjs of type

public class TestObj
{
    public List<int> Ints;
}

How do i perform a Linq query that returns an object in the list if the case is that a given integer x occurs n times, and returns null if not? Something like this:

ListOfTestObjs.FirstOrDefault(l => l.Ints == x occurs 3 times in Ints)

Thanks in advance

Answer 1

如果x是您要查找的数字， n是内部集合中应出现的次数：

ListOfTestObjs.FirstOrDefault(l => l.Ints.Count(i => i == x) == n);