Succintly doing string operations using LINQ and regex

gistfile1.txt

var reg = new Regex(@"(\S+) \({([ \d]+)}\)");
var myStr = @"NULL ({ 8 9 36 37 }) John ({ 1 }) Loizou ({ 2 3 }) delves ({ 4 }) into ({ 5 })";

var lines = reg.Matches(myStr).Cast<Match>().Select(m =>
{
    var prefix = m.Groups[1];
    var nums = m.Groups[2].Value.Split().Where(s => !string.IsNullOrWhiteSpace(s));
    return string.Format("{0} {1}_", prefix, string.Join(",", nums));
});
Console.WriteLine(string.Join(Environment.NewLine, lines));