using System;
using System.Text.RegularExpressions;

public class Test
{
	public static void Main()
	{
        string pattern = @",(?=[^}]*(?:,|$))";
        string input = @"""Key1""=123,""Key2""=""abc"",""key3""={""subkey1""=12,""subkey2""=""cd""},""key4""=456";

      string[] result = Regex.Split(input, pattern, 
                                    RegexOptions.IgnoreCase,
                                    TimeSpan.FromMilliseconds(500));
      for (int ctr = 0; ctr < result.Length; ctr++) 
      {
         Console.WriteLine("'{0}'", result[ctr]);

      }
	}
}