using System; using System.Globalization; using System.Linq; using System.Collections.Generic; using System.Threading; public class Test { public static void Main() { int day = 1; string dayStr = day.ToString("D2"); Console.WriteLine("ToString:" + dayStr); dayStr = "1"; dayStr = dayStr.PadLeft(2, '0'); Console.WriteLine("PadLeft:" + dayStr); } }