Unhandled System.StackOverflowException when using regex in ASP.NET MVC

Question

Hey

I'm using a regular expression to check the format of a supplied date in my ASP.NET MVC exception. However, every time I run it the action the web server crashes and Visual Studio reports and unhandled System.StackOverflowException

//If the supplied date does not match the format yyyy-mm-dd
//Regex taken from www.regexlib.com
if(!Regex.Match(date, "^((((19|20)(([02468][048])|([13579][26]))-02-29))|((20[0-9][0-9])|(19[0-9][0-9]))-((((0[1-9])|(1[0-2]))-((0[1-9])|(1\\d)|(2[0-8])))|((((0[13578])|(1[02]))-31)|(((0[1,3-9])|(1[0-2]))-(29|30)))))$").Success)
{
    ModelState.AddModelError("Date", "Date is in an invalid format. It must in the format yyyy-mm-dd");
}

Has anybody come across this before?

Answer 1

You don't need a regular expression to check DateTime formats, use the DateTime.TryParseExact method:

Converts the specified string representation of a date and time to its DateTime equivalent. The format of the string representation must match a specified format exactly. The method returns a value that indicates whether the conversion succeeded.

Here is an example of how to use it:

DateTime dateTime;

if (!DateTime.TryParseExact(
    yourString, 
    "yyyy-MM-dd", 
    CultureInfo.InvariantCulture, 
    DateTimeStyles.None, 
    out dateTime))
{
     ModelState.AddModelError(
      "Date", 
      "Date is in an invalid format. It must in the format yyyy-mm-dd");
}

I am not sure why your regular expression is creating problems but I think it would be best to avoid the problem all together here by using the proper solution for DateTime validation.