Count of matching elements in a list and array

Question

I have a list and an array. I want to find out the number/count of elements in the array that match those in the list

List<int> list = new List<int>{ 1, 2, 3, 4 };

int[] array = new int[] { 1, 2 };

Since the two matching elements are 1 and 2, I am expecting a result of count 2. Can someone please point me in the right direction?

Answer 1

You can use:

int matches = list.Intersect(array).Count();

Note that this will only work if the list and array only contain unique values.

Answer 2

You can use a little Linq with the Count extension method:

var count = array.Count(list.Contains);

Or if you know that there are no duplicate values in the the array, you can use the Intersect method:

var count = array.Intersect(list).Count();