Validate a DateTime in C#

I doubt I am the only one who has come up with this solution, but if you have a better one please post it here. I simply want to leave this question here so I and others can search it later.

I needed to tell whether a valid date had been entered into a text box and this is the code that I came up with. I fire this when focus leaves the text box.

try
{
    DateTime.Parse(startDateTextBox.Text);
}
catch
{
    startDateTextBox.Text = DateTime.Today.ToShortDateString();
}

From stackoverflow

• DateTime.TryParse This I believe is faster and it means you dont have to use ugly try/catches :)

  e.g

  DateTime temp;
  if(DateTime.TryParse(startDateTextBox.Text, out temp))
  //yay
  else
  // :(
  

  Alex Fort : You beat me to it ;)

  qui : Fastest gun in the west ;)

• I would use the DateTime.TryParse() method: http://msdn.microsoft.com/en-us/library/system.datetime.tryparse.aspx

• Don't use exceptions for flow control. Use DateTime.TryParse and DateTime.TryParseExact. Personally I prefer TryParseExact with a specific format, but I guess there are times when TryParse is better. Example use based on your original code:

  DateTime value;
  if (!DateTime.TryParse(startDateTextBox.Text, out value))
  {
      startDateTextox.Text = DateTime.Today.ToShortDateString();
  }
  

  Reasons for preferring this approach:

  • Clearer code (it says what it wants to do)
  • Better performance than catching and swallowing exceptions
  • This doesn't catch exceptions inappropriately - e.g. OutOfMemoryException, ThreadInterruptedException. (Your current code could be fixed to avoid this by just catching the relevant exception, but using TryParse would still be better.)

• What about using TryParse?

• A problem with using DateTime.TryParse is that it doesn't support the very common data-entry use case of dates entered without separators, e.g. 011508.

  Here's an example of how to support this. (This is from a framework I'm building, so its signature is a little weird, but the core logic should be usable):

      private static readonly Regex ShortDate = new Regex(@"^\d{6}$");
      private static readonly Regex LongDate = new Regex(@"^\d{8}$");
  
      public object Parse(object value, out string message)
      {
          msg = null;
          string s = value.ToString().Trim();
          if (s.Trim() == "")
          {
              return null;
          }
          else
          {
              if (ShortDate.Match(s).Success)
              {
                  s = s.Substring(0, 2) + "/" + s.Substring(2, 2) + "/" + s.Substring(4, 2);
              }
              if (LongDate.Match(s).Success)
              {
                  s = s.Substring(0, 2) + "/" + s.Substring(2, 2) + "/" + s.Substring(4, 4);
              }
              DateTime d = DateTime.MinValue;
              if (DateTime.TryParse(s, out d))
              {
                  return d;
              }
              else
              {
                  message = String.Format("\"{0}\" is not a valid date.", s);
                  return null;
              }
          }
  
      }
  

  Matt : I am not worried about seporators in my case because I am using a Masked Text Box, but I can see how that would be handy in other situations I may encounter with this app.