示例：更改日期格式

        static string MDYToDMY(string input)
        {
            return Regex.Replace(input,"\\b(?<month>\\d{1,2})/(?<day>\\d{1,2})/(?<year>\\d{2,4})\\b","${day}-${month}-${year}");
        }
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using System;
using System.Globalization;
using System.Text.RegularExpressions;

public class Class1
{
   public static void Main()
   {
      string dateString = DateTime.Today.ToString("d",DateTimeFormatInfo.InvariantInfo);
      string resultString = MDYToDMY(dateString);
      Console.WriteLine("Converted {0} to {1}.",dateString,resultString);
   }

   static string MDYToDMY(string input) 
   {
        return Regex.Replace(input,"${day}-${month}-${year}");
   }

}