using System;

    using System.Collections.Generic;

    using System.Linq;

    using System.Text.RegularExpressions;

    using System.Threading;

    using System.Threading.Tasks;

​

public class Program

{

    public static void Main()

    {

    string value = @"30-

    150 Kraków, Polska";

​

    var postCode = Regex.Match(value, @"^([0-9][0-9]-[0-9][0-9][0-9])");

​

    Console.WriteLine(postCode.ToString());  

  }

}