Analyzer.cs

public static class Analyzer
{
    public static bool HasValidOpeningClosingBrackets(string input)
    {
        var stack = new Stack<char>(input.Length);
        
        // Test each character in string input
        foreach (var character in input)
        {
            switch (character)
            {
                // When opening bracket, push it in stack
                case '{':
                case '[':
                case '(':
                    stack.Push(character);
                    break;

                // When closing bracket, pop it and test it
                case '}':
                case ']':
                case ')':
                    var stored = stack.Pop();
                    // If the popped item does not match, check has failed
                    if (stored == '{' && character != '}' ||
                        stored == '[' && character != ']' ||
                        stored == '(' && character != ')')
                    {
                        return false;
                    }
                    break;
                default:
                    break;
            }
        }

        // Check hasn't failed yet, input is okay
        return true;
    }
}