new Regex(^\d+$\n+, RegexOptions.Multiline) : Regular Expression « Regular Expression « C# / CSharp Tutorial

1. C# / CSharp Tutorial
2. Regular Expression
3. Regular Expression

using System;
using System.Collections.Generic;
using System.Globalization;
using System.Text;
using System.Text.RegularExpressions;
using System.Reflection;

public class MainClass{

   public static void Main(){
        Regex r = new Regex(@"(^\d+$\n)+", RegexOptions.Multiline);
        Console.WriteLine(r.Match("987987\n129821").Value);
   }
}

987987