Question

I have this class called Variables which has multiple members and one of it is called Name which is a string. Supposed I have a List<Variables>. This has Namesof X, Y, Y, Z.

string variableName = 'Y';

int _totalCount = (from p in variableList
                    where p.Name == variableName
                    select p.Name).Count();

int _totalCount2 = variableList.Select(x => x.Name == variableName).Count();

Question: Why is _totalCount returns 2 (which is what I want) while _totalCount2 returns 4?

Answer 1

Because Select is not doing what you think it does: it’s a projection, not a filter.
The expression x => x.Name == variableName is calculated for each item on your list. You’ll get {False, True, True, False}. Then the Count() gets called on the result, returning 4.

Filtering is done with the Where method that takes a predicate:

int _totalCount2 = variableList.Where(x => x.Name == variableName).Count();