ParseTime.cs

int ParseTime(string input)
{
  var totalMinutes = 0;
  
  input = Regex.Replace(input.ToLower(), "[^\\d|m|h]", string.Empty);
  
  var hoursMatch = Regex.Match(input, "(?<Hours>\\d+)h");
  
  if (hoursMatch.Success)
  {
    totalMinutes += int.Parse(hoursMatch.Groups["Hours"].Value) * 60;
  }
  
  var minutesMatch = Regex.Match(input, "(?<Minutes>\\d+)m");
  
  if (minutesMatch.Success)
  {
    totalMinutes += int.Parse(minutesMatch.Groups["Minutes"].Value);
  }
  
  if ((!hoursMatch.Success && !minutesMatch.Success) || totalMinutes > (24 * 60))
  {
    throw new FormatException();
  }
  
  return totalMinutes;
}