I am trying to validate a date entered into a text box. There is an input mask on the textbox which forces input of xx/xx/xxxx. I am trying to use a regular expression valid
This isn't really an answer, but couldn't you use DateTime.Parse or DateTime.TryParse to check that the date is correct?
Either that or use a DateTime control to make sure it's impossible to enter data that isn't a DateTime. There's lots of JavaScript out there on this subject.