DateTime.TryParse for only a Time parameter?

Question

I am writing a service that calls a method at 4pm and 5am. I would like to keep these times from being hard coded and so I would like to have put them in my appconfig.

Here is the code I have:

public bool CheckTime() 
        {
            DateTime startTime;
            DateTime endTime; 

            DateTime.TryParse(ConfigurationManager.AppSettings["ProcessingStartTime"], out startTime);
            DateTime.TryParse(ConfigurationManager.AppSettings["ProcessingEndTime"], out endTime);

            if(DateTime.Now.TimeOfDay.Equals(startTime) || DateTime.Now.TimeOfDay.Equals(endTime))
                return true;
            else
                return false;
        }

But, since I only want to store the time as a string (something as easy as "4:00pm") how do I parse and encapsulate JUST the time in a DateTime object? Or is there another object? I don't care about the date, it just has to be M-F of any given week of any given year.

Thanks guys.

Answer 1

You can use TryParseExact with an appropriate format string, and then ignore the date. There's no nice encapsulation for "just a time" in .NET. However, there's an alternative - I've been working hard on Noda Time which has the LocalTime type for just this purpose:

// "Traditional" way
LocalTime time;
if (LocalTime.TryParseExact(text, "h:mmtt", out time))
{
    ...
}

// Preferred way

private static readonly LocalTimePattern TimePattern = 
    LocalTimePattern.CreateWithInvariantInfo("h:mmtt");
...

ParseResult<LocalTime> parseResult = TimePattern.Parse(text);
if (parseResult.Success)
{
    LocalTime time = parseResult.Value;
    ...
}

Two side-notes:

• It's almost never appropriate to ignore the return value from DateTime.TryParse (or any other TryParse method) - do you really want to use DateTime.MinValue if there's a problem with the data? There are cases where the default value is appropriate, but they're pretty rare

• Please try to avoid code of the form:

  if (condition)
      return true;
  else
      return false;
  

  This is much more clearly written as:

  return condition;
  

Answer 2

I've had a hard time doing the tryparse (even w/ TryParseExact) so I wrote a regex:

Regex checkTime = new Regex(@"^(?i)(0?[1-9]|1[0-9]|2[0-4]):([0-5][0-9])(:[0-5][0-9])?( AM| PM)?$");

And you can validate your time with this:

checkTime.IsMatch(str);

This will work for these format (case insensitive):

• 08:09:00 AM
• 08:09 AM
• 8:30 AM
• 8:30:59

You can check it here

Hope this helps