Найти в строке количество слов, начинающихся с буквы "b"

            
            string str = "aaa sfd bfs sdf bsfs";
            var count = str.Split(' ', '!', '.', ',').Count(s => s[0] == 'b');

string str = @"Did you know...
... that the truncated spire of St Paul's Church, Seacombe (pictured during reconstruction) was restored to its original height using a stainless-steel frame?
... that in the 1960s, Inuit musician Willie Thrasher formed Inuvik's first rock 'n' roll band?
... that several other nations also expressed their interest in participating in Combined Task Force 150 in some way when a Pakistani admiral took its command?
... that approximately 28,000 topographic names were changed from their native names to new Turkified renditions under various government policies?
... that George Billman found that an infusion of omega-3 fatty acids prevented ventricular fibrillation in dogs otherwise susceptible to it?
... that the Western Australian shrub Lechenaultia formosa is renowned for its red, orange, or yellow flowers?
... that Galadriel Stineman is named after the elven queen in The Lord of the Rings?";
Console.WriteLine(Regex.Matches(str, @"\bb", RegexOptions.IgnoreCase).Count);
foreach (Match match in Regex.Matches(str, @"\bb\w+", RegexOptions.IgnoreCase))
    Console.WriteLine(match.Value);
Console.ReadKey();