如何检查字符串是否包含一定数量的字母和数字C#

using System;
using System.Text.RegularExpressions;

class Program
{
    static void Main()
    {
        string input = "Abc123";
        int requiredLetterCount = 2;
        int requiredDigitCount = 2;

        bool isValid = CheckString(input, requiredLetterCount, requiredDigitCount);
        Console.WriteLine(isValid ? "字符串符合要求" : "字符串不符合要求");
    }

    static bool CheckString(string input, int requiredLetterCount, int requiredDigitCount)
    {
        int letterCount = 0;
        int digitCount = 0;

        foreach (char c in input)
        {
            if (char.IsLetter(c))
            {
                letterCount++;
            }
            else if (char.IsDigit(c))
            {
                digitCount++;
            }
        }

        return letterCount >= requiredLetterCount && digitCount >= requiredDigitCount;
    }
}