VB Classic Logical Operators

VB Classic logical operators:

VB Classic never short circuits. Given the expression this or that as well as this and that, if this evaluates to false, then that is still executed.

Using the Logical Not Operator

You can use the not operator in many contexts. One of my favorite uses for it is to toggle boolean properities with a single line of code:

BooleanProperty = Not BooleanProperty

VB6 Working Demo

The following demo uses the not operator to toggle the visible property of a PictureBox from a button.

1. Create a new form and place a button and a PictureBox on it. Add a picture to the PictureBox with the Picture property.
    
   
    
2. Edit the Click event and alter it as follows below (double click the button). Your PictureBox should be named Picture1, but if it's not, use the correct object name.
    
   Private Sub Command1_Click()
       Picture1.Visible = Not Picture1.Visible
   End Sub
    
3. Run the application and test. Select Run| Start and click the button. You'll notice the picture toggles between visible and not visible with a single line of code.

VB Classic Short Circuting Example:

In the following example, if VB Classic supported short circuting, the That function would never execute. It's interesting to note that VB.Net has introduced two new operators to support short cicuiting: AndAlso and OrElse but you'll have to move to VB.Net to take advantage of them.

Function This()
    MsgBox ("The This function executed.")
    This = False
End Function

Function That()
    MsgBox ("The That function executed!")
    That = True
End Function

Private Sub Command0_Click()
    'Notice both the This and That functions execute
    'even though the This Function returned False.
    If This And That Then
        MsgBox ("hi")
    End If
End Sub