Paul Vick on two new operators in VB Whidbey

In a recent post to his blog, Paul Vick discusses the new IsNot Operator (and the history/rational behind the Is operator), which allows you to write;

 If myString IsNot Nothing Then

instead of

 If Not myString Is Nothing Then

and then, in another post, he covers the new TryCast operator (which is like C#'s 'as' operator), which will allow you to save a bit of extra work (and produce a slight perf improvement in some situations) when checking to see if an object can be cast to a specific type .... allowing you to write;

 Sub Print(ByVal o As Object)
    Dim PrintableObject As IPrintable _
        = TryCast(o, IPrintable)
    If PrintableObject IsNot Nothing Then
        PrintableObject.Print()
    End If
    ...
End Sub

instead of the slightly less efficient

 Sub Print(ByVal o As Object)
    Dim PrintableObject As IPrintable
    If TypeOf o Is IPrintable Then
        PrintableObject = CType(o, IPrintable)
        PrintableObject.Print()
    End If
    ...
End Sub

Comments

• Anonymous
  March 02, 2004
  First one should have been Aint. This way, we could get into childish arguments:
  
  If myThing Is IsNot Is IsNot Nothing then...
  'Says you...
  End If
  
  The TryCast will be cool, though. It's been one of the very few items (As) I've really started to like in C# and miss in VB.
  
  TTFN- Kent
• Anonymous
  March 02, 2004
  Both of those look cool to me.
• Anonymous
  March 02, 2004
  Hi,
  
  I am doing a project on forex. my client's requirement is that the currency values should be update daily by the system itself.
  I am developing the system in VB/Access.
  There is website of Thomas Cook which contains the table of all currency values. The link as below :
  http://www.thomascook.co.in/tc/user/forex/forexcurrencyrates.jsp?jsessionid=2580261077697883828
  
  So, my problem I want the currency values, in the above link to update my 'Currency_Master' Table in MS-Access when click a command button.
  
  Please help or provide some code for it on
  shivnil2@rediffmail.com.
  
  thank you,
  with regards,
  shivnil
• Anonymous
  March 04, 2004
  
  Great, now we can finally start to write some "proper" code:
  
  If Not something IsNot somethingElse Then
  ...
  End If
  
  :)
  
• Anonymous
  March 04, 2004
  The IsNot operator seems a bit pointless but the TryCast is quite a nice touch, even though I can't imagine that the performance improvement will be that significant.
• Anonymous
  March 04, 2004
  IsNot is equivalent to using <> instead of not(x=y), so to my mind it fills a little gap.
  
  TryCast is extra sweet if you have to check for nothing anyway.
• Anonymous
  March 05, 2004
  how do i move an image around the page like it is moving?
• Anonymous
  March 07, 2004
  i make project by bv5 with data base
  this db i well make password for he
  how 2 open this data base in my proeject
  when press f5 i c msg
  inviled password
  please f u can send 2 my this code
  thank 4 help
• Anonymous
  March 08, 2004
  teaching VB6
• Anonymous
  March 09, 2004
  Why it has to be such horribe looking mess? For example:
  
  If myString IsNot Nothing Then
  
  Could be:
  if (myString) { }
  
  and
  
  If myString Is Nothing Then
  
  could be:
  if (!myString) { }
  
  Much more clean and simpler.