Trim last wrod regexp "Blah Blah Blah Bl..." -> "Blah Blah Blah..."

TrimLastWord.cs

using System.Text.RegularExpressions;

public static class TrimLastWord{
  private static Regex _trimLastWord = new Regex(@"\s+?(\S+)?$");
  private static string TrimLastWord(this string str, int maxLength, string extra="...")
  {            
    if (str?.Length > maxLength)
        return $"{_trimLastWord.Replace(str.Substring(0, maxLength), "")}{extra}";
    return str;
  }
}