static void Main(string[] args)
{
     var strwords = FilterWords("I AM coming from FORGET CODE !  you know ? ");
    foreach (string str in strwords)
        Console.WriteLine(str);
    Console.ReadLine();
}

static IEnumerable<string> FilterWords(string str)
{           
    var upper =  str.Split(' ')
                .Where(s => String.Equals(s, s.ToUpper(),
                            StringComparison.Ordinal));

    return upper;
}