[RESOLVED] [02/03] protected vs Dim

[vishalmarya]

if i define a webusercontrol :

lets say ,

dim withevents Webusercontrol11 as Webusercontrol1


then use of any of its public property or method , generates an error

"Object reference not set to an instance of an object ."

if i use ,

protected withevents Webusercontrol11 as Webusercontrol1

it works fine

why ?

[Coool]

Dim means Private. And Protected mean variable can be accessible to It class and it's immediate child.

[penagate]

Dim's a legacy BASIC keyword. You should use the explicit scope modifiers.

[vishalmarya]

i know the basic difference regarding inheritance .

but that does not answer my question.

[vishalmarya]

ok i got this one.

the answer lies in how aspx pages are processed.

http://msdn2.microsoft.com/en-us/lib...ontrols_topic4


When an aspx page is requested , a class is automatically created which is derived from the Web page's code-behind class (apx.vb).

this new class constructs the Web page's control hierarchy.

so any control which is declared as dim/private , will not appear in this hierarchy and hence reference to any such control will result in

"NullReferenceException" error .

so all controls on a web page needs to be declared protected ( at least )

[kleinma]

Dim's a legacy BASIC keyword. You should use the explicit scope modifiers.

it is??

then what do you use to declare a variable at the procedure level?


as in:

Private Sub test()
        Dim A As String         'VALID  
        Private B As String     'ERROR
        Friend C As String      'ERROR
        Public D As String      'ERROR
        Protected E As String   'ERROR
End Sub

[penagate]

Whoops. I meant at class level.

[kleinma]

I guess you could consider it legacy at the class level, however I don't have any gripes about using Dim at the class level (others might)

When you use Dim at the class level, VB automatically assumes its private, infact if you mouse over it, you will see that it has a private modifier.