using System;
using System.Text.RegularExpressions;

public class Test
{
  public static void Main()
  {
    const string line = @"125,45.124.890,45,32,67.456";
    MatchCollection matches = Regex.Matches(line, 
      @"(?!0\d)\d{1,3}(?:\.\d{3})*(?:\,\d+(?![\d\.]))?");
    foreach(Match match in matches)
    {
      foreach (Capture capture in match.Captures)
      {
        Console.WriteLine(capture.Value);
      }
    }
  }
}