Hi all,
Ok - I've used the word gramatically - which I'm sure is incorect, however I
mean when VS2005 lists "warnings" like this one:
Warning 1 Variable 'Command' is used before it has been assigned a value. A
null reference exception could result at runtime.
Warning 2 Variable 'Connection' is used before it has been assigned a value.
A null reference exception could result at runtime.
Warning 3 Variable 'Command' is used before it has been assigned a value. A
null reference exception could result at runtime.
Warning 4 Variable 'Connection' is used before it has been assigned a value.
A null reference exception could result at runtime.
Now, in my code I often do this within the "catch" part of a try..catch if
I've used a database connection/command in the "Try" section;
' tidy up
If Command Is Nothing <> False Then
Command.Dispose ()
Command = Nothing
End If
If Connection Is Nothing <> False Then
Connection.Clos e()
Connection = Nothing
End If
The reason I do this, I believe is for tidyness, its quite possible that if
an exception was caused I may have already created my connection object,
and/or my Command object, therefore I test to see if they are "something" ,
and if so deal with them appropriately..
Of course, now with its new gadgets VS reports problems because I've not
"something' d" them in the "Catch" although I have in the "Try"...
Any suggestions - is my coding bad? Is there a better way? Any info
appreciated, I'm trying to go for good coding practices you see :o)
Rob
6  1217 
One comment, is that when you are testing that the result of a boolean
expression is not equal to false - that is really confusing to read. A more
readable way is:
If Command Is Nothing = True Then
And, better yet:
If Command Is Nothing Then
Which is the most readable out of all of them.
Now, in all of the cases above, your If statement will execute, which is not
what you want, since you will get a nullreferenceex ception.
Which proves my point as to just how confusing writing code like that is.
Now, the compiler can only do so much in figuring out your code. It may be,
that your code is written in such a way, that an object is always assigned
before you use it. If you want to get rid of the warning, always assign the
variable, even if it is to nothing.
And lastly, you do not need to set the variables to Nothing. That was
something you had to do in VB6.
"Rob Meade" <te************ **@edaem.bbor> wrote in message
news:0a******** *******@text.ne ws.blueyonder.c o.uk... Hi all,
Ok - I've used the word gramatically - which I'm sure is incorect, however
I mean when VS2005 lists "warnings" like this one:
Warning 1 Variable 'Command' is used before it has been assigned a value.
A null reference exception could result at runtime.
Warning 2 Variable 'Connection' is used before it has been assigned a
value. A null reference exception could result at runtime.
Warning 3 Variable 'Command' is used before it has been assigned a value.
A null reference exception could result at runtime.
Warning 4 Variable 'Connection' is used before it has been assigned a
value. A null reference exception could result at runtime.
Now, in my code I often do this within the "catch" part of a try..catch if
I've used a database connection/command in the "Try" section;
' tidy up
If Command Is Nothing <> False Then
Command.Dispose ()
Command = Nothing
End If
If Connection Is Nothing <> False Then
Connection.Clos e()
Connection = Nothing
End If
The reason I do this, I believe is for tidyness, its quite possible that
if an exception was caused I may have already created my connection
object, and/or my Command object, therefore I test to see if they are
"something" , and if so deal with them appropriately..
Of course, now with its new gadgets VS reports problems because I've not
"something' d" them in the "Catch" although I have in the "Try"...
Any suggestions - is my coding bad? Is there a better way? Any info
appreciated, I'm trying to go for good coding practices you see :o)
Rob
You have a few options:
1. You can ignore warnings which you are certain are not going to cause a
problem. Not a bad idea. After all, a warning is not a show-stopper, but it
does bring your attention to a potential problem.
2. You can turn off certain types of warnings in Tools|Options.
3. You can write code that the IDE prefers you to write. Not a bad idea.
There are good reasons why these warnings are raised, and adapting good
coding practices is always a help.
4. Some combination of the above which suits your specific personality
and/or needs.
--
HTH,
Kevin Spencer
Microsoft MVP
..Net Developer
A watched clock never boils.
"Rob Meade" <te************ **@edaem.bbor> wrote in message
news:0a******** *******@text.ne ws.blueyonder.c o.uk... Hi all,
Ok - I've used the word gramatically - which I'm sure is incorect, however
I mean when VS2005 lists "warnings" like this one:
Warning 1 Variable 'Command' is used before it has been assigned a value.
A null reference exception could result at runtime.
Warning 2 Variable 'Connection' is used before it has been assigned a
value. A null reference exception could result at runtime.
Warning 3 Variable 'Command' is used before it has been assigned a value.
A null reference exception could result at runtime.
Warning 4 Variable 'Connection' is used before it has been assigned a
value. A null reference exception could result at runtime.
Now, in my code I often do this within the "catch" part of a try..catch if
I've used a database connection/command in the "Try" section;
' tidy up
If Command Is Nothing <> False Then
Command.Dispose ()
Command = Nothing
End If
If Connection Is Nothing <> False Then
Connection.Clos e()
Connection = Nothing
End If
The reason I do this, I believe is for tidyness, its quite possible that
if an exception was caused I may have already created my connection
object, and/or my Command object, therefore I test to see if they are
"something" , and if so deal with them appropriately..
Of course, now with its new gadgets VS reports problems because I've not
"something' d" them in the "Catch" although I have in the "Try"...
Any suggestions - is my coding bad? Is there a better way? Any info
appreciated, I'm trying to go for good coding practices you see :o)
Rob
"Marina" wrote ... One comment, is that when you are testing that the result of a boolean
expression is not equal to false - that is really confusing to read. A
more readable way is:
If Command Is Nothing = True Then
And, better yet:
If Command Is Nothing Then
Hi Marina,
I understand what you are saying, and thank you for the reply, however, in
my example:
If Command Is Nothing <> False Then
Command.Dispose ()
Command = Nothing
End If
I would then have do add more code, ie,
If Command Is Nothing Then
' do nothing
Else
Command.Dispose
Command = Nothing
End If
Easier to read - but more code...
Now, in all of the cases above, your If statement will execute, which is
not what you want, since you will get a nullreferenceex ception.
But this is why I'm testing it? Am I not saying in the test, if the object
is "something" then kill it off? ie, if its "nothing" (null?) then dont
worry...skip right past...
Which proves my point as to just how confusing writing code like that is.
I'm obviously missing something, it makes sense to me - is what I've replied
with above here wrong then?
Now, the compiler can only do so much in figuring out your code. It may
be, that your code is written in such a way, that an object is always
assigned before you use it. If you want to get rid of the warning, always
assign the variable, even if it is to nothing.
The full chunk is as follows:
Public Function TruncateDatabas e() As Boolean
' declare variables
Dim Connection As SqlConnection
Dim Command As SqlCommand
Dim Result As Boolean
' exception handling
Try
' create and open our database connection
Connection = New
SqlConnection(C onfigurationMan ager.AppSetting s("Webmasters") )
Connection.Open ()
' create and define our command object
Command = New SqlCommand
Command.Connect ion = Connection
Command.Command Type = CommandType.Tex t
Command.Command Text = "TRUNCATE TABLE Webmasters"
' execute
Command.Execute NonQuery()
' tidy up
Command.Dispose ()
Command = Nothing
Connection.Clos e()
Connection = Nothing
' set result
Result = True
Catch ex As Exception
' TODO: Error handling
' tidy up
If Command Is Nothing <> False Then
Command.Dispose ()
Command = Nothing
End If
If Connection Is Nothing <> False Then
Connection.Clos e()
Connection = Nothing
End If
' set flag
Result = False
End Try
' return result
Return Result
End Function
As per my initial post, I only actually set a value to those objects in the
"Try" block, hence the warning...as you suggested, setting them to nothing
at the top outside of Try would obviously clear these up.
And lastly, you do not need to set the variables to Nothing. That was
something you had to do in VB6.
I do that for completeness, I read/heard about .net clearing up after itself
as and when it deems appropriate, I just like to save it the trouble :)
Rob
"Kevin Spencer" wrote... 1. You can ignore warnings which you are certain are not going to cause a
problem. Not a bad idea. After all, a warning is not a show-stopper, but
it does bring your attention to a potential problem.
I love 'em - I think its one of my favourite things thus far between
2003/2005 - I've always been very task orientated, so for me this is dead
handy, oh look a long list of stuff to sort out :o)
2. You can turn off certain types of warnings in Tools|Options.
nah..
3. You can write code that the IDE prefers you to write. Not a bad idea.
There are good reasons why these warnings are raised, and adapting good
coding practices is always a help.
Sounds like a good idea.
4. Some combination of the above which suits your specific personality
and/or needs.
3 for me I think :o)
Cheers Kevin,
Rob
re: I understand what you are saying, and thank you for the reply, however, in my example:
If Command Is Nothing <> False Then
Command.Dispose ()
Command = Nothing
End If
I would then have do add more code, ie,
Wouldn't :
If Command Then
Command.Dispose ()
Command = Nothing
End If
work better ?
In C#, that works, too :
if (Command) {
Command.Dispose ();
Command = null;
}
Juan T. Llibre, ASP.NET MVP
ASP.NET FAQ : http://asp.net.do/faq/
Foros de ASP.NET en Español : http://asp.net.do/foros/
=============== =============== ========
"Rob Meade" <te************ **@edaem.bbor> wrote in message
news:BT******** ******@text.new s.blueyonder.co .uk... "Marina" wrote ...
One comment, is that when you are testing that the result of a boolean expression is
not equal to false - that is really confusing to read. A more readable way is:
If Command Is Nothing = True Then
And, better yet:
If Command Is Nothing Then
Hi Marina,
I understand what you are saying, and thank you for the reply, however, in my example:
If Command Is Nothing <> False Then
Command.Dispose ()
Command = Nothing
End If
I would then have do add more code, ie,
If Command Is Nothing Then
' do nothing
Else
Command.Dispose
Command = Nothing
End If
Easier to read - but more code...
Now, in all of the cases above, your If statement will execute, which is not what you
want, since you will get a nullreferenceex ception.
But this is why I'm testing it? Am I not saying in the test, if the object is
"something" then kill it off? ie, if its "nothing" (null?) then dont worry...skip right
past...
Which proves my point as to just how confusing writing code like that is.
I'm obviously missing something, it makes sense to me - is what I've replied with above
here wrong then?
Now, the compiler can only do so much in figuring out your code. It may be, that your
code is written in such a way, that an object is always assigned before you use it. If
you want to get rid of the warning, always assign the variable, even if it is to
nothing.
The full chunk is as follows:
Public Function TruncateDatabas e() As Boolean
' declare variables
Dim Connection As SqlConnection
Dim Command As SqlCommand
Dim Result As Boolean
' exception handling
Try
' create and open our database connection
Connection = New SqlConnection(C onfigurationMan ager.AppSetting s("Webmasters") )
Connection.Open ()
' create and define our command object
Command = New SqlCommand
Command.Connect ion = Connection
Command.Command Type = CommandType.Tex t
Command.Command Text = "TRUNCATE TABLE Webmasters"
' execute
Command.Execute NonQuery()
' tidy up
Command.Dispose ()
Command = Nothing
Connection.Clos e()
Connection = Nothing
' set result
Result = True
Catch ex As Exception
' TODO: Error handling
' tidy up
If Command Is Nothing <> False Then
Command.Dispose ()
Command = Nothing
End If
If Connection Is Nothing <> False Then
Connection.Clos e()
Connection = Nothing
End If
' set flag
Result = False
End Try
' return result
Return Result
End Function
As per my initial post, I only actually set a value to those objects in the "Try" block,
hence the warning...as you suggested, setting them to nothing at the top outside of Try
would obviously clear these up.
And lastly, you do not need to set the variables to Nothing. That was something you had
to do in VB6.
I do that for completeness, I read/heard about .net clearing up after itself as and when
it deems appropriate, I just like to save it the trouble :)
Rob
The same for Connection, btw :
If Connection Then
Connection.Clos e()
Connection = Nothing
End If
Juan T. Llibre, ASP.NET MVP
ASP.NET FAQ : http://asp.net.do/faq/
Foros de ASP.NET en Español : http://asp.net.do/foros/
=============== =============== ========
"Juan T. Llibre" <no***********@ nowhere.com> wrote in message
news:Od******** ******@TK2MSFTN GP12.phx.gbl... re: I understand what you are saying, and thank you for the reply, however, in my example:
If Command Is Nothing <> False Then
Command.Dispose ()
Command = Nothing
End If
I would then have do add more code, ie,
Wouldn't :
If Command Then
Command.Dispose ()
Command = Nothing
End If
work better ?
In C#, that works, too :
if (Command) {
Command.Dispose ();
Command = null;
}
Juan T. Llibre, ASP.NET MVP
ASP.NET FAQ : http://asp.net.do/faq/
Foros de ASP.NET en Español : http://asp.net.do/foros/
=============== =============== ========
"Rob Meade" <te************ **@edaem.bbor> wrote in message
news:BT******** ******@text.new s.blueyonder.co .uk... "Marina" wrote ...
One comment, is that when you are testing that the result of a boolean expression is
not equal to false - that is really confusing to read. A more readable way is:
If Command Is Nothing = True Then
And, better yet:
If Command Is Nothing Then
Hi Marina,
I understand what you are saying, and thank you for the reply, however, in my example:
If Command Is Nothing <> False Then
Command.Dispose ()
Command = Nothing
End If
I would then have do add more code, ie,
If Command Is Nothing Then
' do nothing
Else
Command.Dispose
Command = Nothing
End If
Easier to read - but more code...
Now, in all of the cases above, your If statement will execute, which is not what you
want, since you will get a nullreferenceex ception.
But this is why I'm testing it? Am I not saying in the test, if the object is
"something" then kill it off? ie, if its "nothing" (null?) then dont worry...skip
right past...
Which proves my point as to just how confusing writing code like that is.
I'm obviously missing something, it makes sense to me - is what I've replied with above
here wrong then?
Now, the compiler can only do so much in figuring out your code. It may be, that your
code is written in such a way, that an object is always assigned before you use it.
If you want to get rid of the warning, always assign the variable, even if it is to
nothing.
The full chunk is as follows:
Public Function TruncateDatabas e() As Boolean
' declare variables
Dim Connection As SqlConnection
Dim Command As SqlCommand
Dim Result As Boolean
' exception handling
Try
' create and open our database connection
Connection = New SqlConnection(C onfigurationMan ager.AppSetting s("Webmasters") )
Connection.Open ()
' create and define our command object
Command = New SqlCommand
Command.Connect ion = Connection
Command.Command Type = CommandType.Tex t
Command.Command Text = "TRUNCATE TABLE Webmasters"
' execute
Command.Execute NonQuery()
' tidy up
Command.Dispose ()
Command = Nothing
Connection.Clos e()
Connection = Nothing
' set result
Result = True
Catch ex As Exception
' TODO: Error handling
' tidy up
If Command Is Nothing <> False Then
Command.Dispose ()
Command = Nothing
End If
If Connection Is Nothing <> False Then
Connection.Clos e()
Connection = Nothing
End If
' set flag
Result = False
End Try
' return result
Return Result
End Function
As per my initial post, I only actually set a value to those objects in the "Try"
block, hence the warning...as you suggested, setting them to nothing at the top outside
of Try would obviously clear these up.
And lastly, you do not need to set the variables to Nothing. That was something you
had to do in VB6.
I do that for completeness, I read/heard about .net clearing up after itself as and
when it deems appropriate, I just like to save it the trouble :)
Rob
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