Get the difference between two lists using LINQ

not in will work for you

var listOfIds = new List<int> {1,2,4};

var query = from item in persons 
            where !listOfIds .Contains( item.id )
            select item;

You can check for more detail : SQL to LINQ ( Case 7 - Filter data by using IN and NOT IN clause)

With Linq in C# you can do the following variants which give the same results:

int[] numbers1 = { 1,2,3,4 };
int[] numbers2 = { 3,4,5,6 };

// Ac V Bc, thus complement of A plus the complement of B
IEnumerable<int> differencesVariant1 = 
numbers1.Except(numbers2).Union(numbers2.Except(numbers1));

// (A V b)c, thus complement of (set A plus set B)
IEnumerable<int> differencesVariant2 = 
numbers1.Union(numbers2).Except(numbers1.Intersect(numbers2));

Console.WriteLine("variant 1:");
foreach (int number in differencesVariant1)
    Console.WriteLine(number);   // prints: 1,2,5,6

Console.WriteLine("variant 2:");
foreach (int number in differencesVariant2)
    Console.WriteLine(number);   // prints: 1,2,5,6

var list1 = new List<int> {1,2,3,4,5};
var list2 = new List<int> {2,3,4,5,6};

list1.Except(list2); //1 - items removed
list2.Except(list1); //6 - items added

You can also use lambda:

var query = persons.Where(item => !listOfIds.Contains(item.Id));