C# code always returns false from DateTime.TryParseExact method

Question

I am working on a C# application. I have below code to validate the date:

private DateTime? ParseUserInputDate(string providedDate)
{
      DateTime validDate;
      var dateFormatIsValid = DateTime.TryParseExact(
        providedDate,
        Constants.DateFormats.UserInput,
        CultureInfo.InvariantCulture,
        DateTimeStyles.None,
        out validDate);
      return dateFormatIsValid ? validDate : (DateTime?)null;
}

When I pass "2/09/2019 12:00:00 AM" as providedDate and UserInput format is "d/M/yyyy", it returns always false. Can someone help me to figure out this issue?

Answer 1

If you want to parse time , you have to mention time part in the pattern; if you have to use several patterns (say, with and without date) you can put them into one TryParseExact :

private DateTime? ParseUserInputDate(string providedDate) {
  // we can simplify the code with a help of out var
  return DateTime.TryParseExact(providedDate,
                                new string[] {
                                  "d/M/yyyy",            // Try date first
                                  "d/M/yyyy h:m:s tt",   // if fails try date and time
                                },
                                CultureInfo.InvariantCulture,
                                DateTimeStyles.None,
                                out var validDate)
    ? validDate
    : (DateTime?) null;
}

...

// Date and Time
Console.WriteLine(ParseUserInputDate("2/09/2019 12:00:00 AM")
  .Value
  .ToString("dd.MM.yyyy HH:mm:ss"));

// Date only
Console.WriteLine(ParseUserInputDate("2/09/2019")
 .Value
 .ToString("dd.MM.yyyy HH:mm:ss"));

Outcome:

02.09.2019 00:00:00
02.09.2019 00:00:00

Answer 2

The format and input are completely different. if you pass "2/09/2019 12:00:00 AM", then change the format to "d/M/yyyy h:mm:ss tt"

    Private static DateTime? ParseUserInputDate(string providedDate)
    {
        DateTime validDate;
        string[] formats = { "d/M/yyyy h:mm:ss tt", "d/M/yyyy" };
        var dateFormatIsValid = DateTime.TryParseExact(
          providedDate,
          formats,
          CultureInfo.InvariantCulture,
          DateTimeStyles.None,
          out validDate);
        return dateFormatIsValid ? validDate : (DateTime?)null;
    }