How to count the occurence of each number in list A that is exist in list B and return zero if not existed?

This is my first question in this community and I would like to get an answer to my problem ,
Suppose that I have two lists A and B:

List<int> listA = new List<int>();
List<int> listB = new List<int>();

listA.Add(1);
listA.Add(2);
listA.Add(8);


listB.Add(1);
listB.Add(1);
listB.Add(1);
listB.Add(2);
listB.Add(2);
listB.Add(2);
listB.Add(2);

I would like to count the occurrences of each element in listB that already existed in listA and add zero if does not exist:

This is what I’ve tried:

var result = listB.GroupBy(x => x).ToDictionary(k => k.Key, v => v.Count());
foreach(var res in result.Values)
    Console.WriteLine(res); // it will print only {3,4} 

The expected result will be :

// { 3,4,0}  => 3 is the occurrences number of 1 , 4 is the occurrences number of 2 ,and 0 is the number occurrences of 8

How can I achieve this result?

>Solution :

I would use the linq .Count() extension, which will count the number of items that satisfy a condition. Yes, this will iterate the list more times than is necessary, but it doesn’t create any unnecessary objects, and it is very readable:

var countOccurences = new List<int>();
        
foreach (var inA in listA)
{
    countOccurences.Add(listB.Count(inB => inB == inA));
}
    
Console.WriteLine(string.Join(", ", countOccurences));

Once you’ve got the loop working, then it should be easy to see that it can be done in a single statement:

var countOccurences = listA.Select(inA => listB.Count(inB => inA == inB));