C# - 如何验证字符串的格式为hh:mm:ss:fff？

using System;
using System.Text.RegularExpressions;

class Program {
    static void Main(string[] args) {
        string timeString = "12:34:56:789";
        Regex regex = new Regex(@"\d{2}:\d{2}:\d{2}:\d{3}");
        if (regex.Match(timeString).Success) {
            Console.WriteLine("The time string is in the correct format.");
        } else {
            Console.WriteLine("The time string is not in the correct format.");
        }
    }
}