block level variables .. when to use them and why??

[Anoj]

Hi All,

As you all know in vb.net we can declare block level
variables. Like :
Dim I As Integer
For I = 1 To 3
Dim N As Long
' N has block scope in VB.NET
N = N + I
Next

Can someone tell me what is the benefit of
doing so ..

Which practice is better ..
1. declaring variables at the top of the function/procedure
2. declaring variables whereever needed

Thanx

Regards,
Anoj Kumar

 

[CT]

Anoj,

The benefit of using block scoped variables is that they go out of scope
once your code exits the block of code in question. I personally think that
makes your code easier to read. Now, you were giving an example with a For
Next loop, but IMO anything is "block scoped" meaning that a variable in a
procedure is local to that procedure. So, with that in mind I think your
code looks cleaner if you declare your variables at the top of the block.

BTW, I has procedure level scope in your example and that is probably your
intention, but if it's only needed as a loop counter, you might consider
this approach:

For I As Integer = 1 To 3

 

[Cor Ligthert]

Anoj,

As attention on CT message,
For i as Integer = 0 to x
Is only working on VBNet newer than 2002.

Just an addition.
The rest I agree complete.

Cor

 

[CT]

For i as Integer = 0 to x

Is only working on VBNet newer than 2002.

Damn, you caught me. No, seriously thanks for poiting it out.

 

[Herfried K. Wagner [MVP]]

So, with that in mind I think your code looks cleaner if you declare your
variables at the top of the block.

I think that decision should be based on personal preference. Variables can
be used only after their declaration, and thus additional scoping inside the
local scope is possible:

\\\

' Variable 'i' cannot be accessed.
....
Dim i As Integer

' Variable 'i' can be accessed.
///

 

[Cor Ligthert]

Herfried,

I think that decision should be based on personal preference. Variables
can be used only after their declaration, and thus additional scoping
inside the local scope is possible:

And is CT allowed to have that?

))

Cor