VB.NET regular expresion for future date

Question

Hi,

I want to validate textbox so that it will accept only future date. Can I have regular expression for the same.

I am using vb.net for coding.

Thanks.

Best Regards, Manoj

Answer 1

Why use a regular expression? Wouldn't it be easier to parse the date entered by the user into a DateTime then compare it to DateTime.Now to ensure that it is greater?

Here is an example:

Imports System

Class Test
    Private Shared Sub Main()
        Console.WriteLine(isFutureDate("5/16/1984"))
        Console.WriteLine(isFutureDate("5/16/2010"))
    End Sub
    
    Private Shared Function isFutureDate(ByVal candidate As String) As Boolean
        Dim future As DateTime
        
        DateTime.TryParse(candidate, future)
        
        Return future > DateTime.Now
    End Function
End Class

Answer 2

I presume you want a regular expression so you can have it valid client side? You'd be better off with a custom validator, with both server side and client side code. You can set the client side code using the ClientValidationFunction property on the custom validator.

For the client side code you'd do embed something like the following script in your page (from the top of my head, not checked)

<script language="JavaScript">
<!--
  function CheckPrime(sender, args)
  {
    var currentDate = new Date();
    var enteredDate = new Date(args.Value);

    if (enteredDate > currentDate)
      args.IsValid = true;
    else
      args.IsValid = false;
  }
// -->
</script>

For server side you'd do the normal check you want in VB. The server check will always run, regardless of the client script results.