Leetcode Valid Parentheses C#

Challenge

Solution

public class Solution {
    public bool balanced(char parenLeft, char parenRight) {
        switch (parenLeft) {
            case '(':
                return parenRight == ')';
                break;
            case '[':
                return parenRight == ']';
                break;
            case '{':
                return parenRight == '}';
                break;
        }
        return false;
    }
    
    public bool IsValid(string s) {
        HashSet<char> openParens = new HashSet<char>(){'(', '{', '['};
        HashSet<char> closeParens = new HashSet<char>(){')', '}', ']'};
        
        Stack<char> parenStack = new Stack<char>();
        for (int i = 0; i < s.Length; i++) {
            if (openParens.Contains(s[i])) {
                parenStack.Push(s[i]);
            } else if (parenStack.Count > 0 && balanced(parenStack.Peek(), s[i])) {
               parenStack.Pop(); 
            } else return false;
        }
        return parenStack.Count == 0;
    }
}