using System;
using System.Text.RegularExpressions;

public class Test
{
	public static void Main()
	{

          
String s = @"[[Hello]]
<tag Text=""my [[Test]] is [[Test2]] for [[Test3]][[Test4]]"">";

Match m  = Regex.Match(s, @"\[\[[^]]*\]\](?<!""[^""]*)");

if (m.Success)
    Console.WriteLine(m.Value); 


	}
}