null reference exception could result at runtime
in [VB.NET]
|
Prev: How to get the list of all SQL Server foreign keys in a database by using Microsoft.SqlServer.Management.Smo ?
Next: How to tell if folder item is file or folder?
From: mp on 7 Apr 2010 14:50 vbnet 2008 express how to avoid the compiler warning: Variable 'ArrayObjects' is used before it has been assigned a value. A null null reference exception could result at runtime. given Dim ArrayObjects() As AcadEntity ....some code... Try ReDim ArrayObjects(0) ArrayObjects(UBound(ArrayObjects)) = oSideLine'(oSideLine is an acad entity) Catch ex As ApplicationException m_Util.Logentry("error " & ex.Message) End Try ....more code...then... Try If ArrayObjects Is Nothing Then <------------here is the warning location at "ArrayObjects" m_Util.Logentry("error ArrayObjects Is Nothing") Else SelectionSetWblock.AddItems(ArrayObjects) End If Catch ex As ApplicationException End Try what should I be doing in such cases (using an array) i wouldn't think you'd do Dim ArrayObjects() As AcadEntity = Nothing like you might with a simple object??? thanks mark
From: Armin Zingler on 7 Apr 2010 15:32 Am 07.04.2010 20:50, schrieb mp: > vbnet 2008 express > how to avoid the compiler warning: > Variable 'ArrayObjects' is used before it has been assigned a value. A null > null > reference exception could result at runtime. > > given > Dim ArrayObjects() As AcadEntity > > ....some code... > > Try > > ReDim ArrayObjects(0) > > ArrayObjects(UBound(ArrayObjects)) = oSideLine'(oSideLine is an acad entity) > > Catch ex As ApplicationException > > m_Util.Logentry("error " & ex.Message) > > End Try > > ....more code...then... > > Try > > If ArrayObjects Is Nothing Then <------------here is the warning location at > "ArrayObjects" > > m_Util.Logentry("error ArrayObjects Is Nothing") > > Else > > SelectionSetWblock.AddItems(ArrayObjects) > > End If > > Catch ex As ApplicationException > > End Try > > > > what should I be doing in such cases (using an array) > > i wouldn't think you'd do Dim ArrayObjects() As AcadEntity = Nothing > > like you might with a simple object??? Well, what is a not-simple object? An array is an object, so you can assign Nothing in the declaration line as you've checked that the warning isn't justified in this case. -- Armin
From: Mr. Arnold on 7 Apr 2010 16:52 mp wrote: > > If ArrayObjects Is Nothing Then <------------here is the warning location at > "ArrayObjects" > You only want to do something, work with the object, if it is 'NOT' null. So you have an if statement checking for the NOT null condition. On the other hand, if the object is never going to be null, then why worry about? It's just a warning message.
From: mp on 7 Apr 2010 17:04 "Mr. Arnold" <Arnold(a)Arnold.com> wrote in message news:Ok%23zQRp1KHA.4724(a)TK2MSFTNGP02.phx.gbl... > mp wrote: >> >> If ArrayObjects Is Nothing Then <------------here is the warning location >> at >> "ArrayObjects" >> > > You only want to do something, work with the object, if it is 'NOT' null. > > So you have an if statement checking for the NOT null condition. > > On the other hand, if the object is never going to be null, then why worry > about? It's just a warning message. ok, i just thought the warning was telling me i was doing something "wrong" and trying to learn best practices thanks Mr Arnold and Armin
From: Phill W. on 8 Apr 2010 08:30
On 07/04/2010 19:50, mp wrote: > how to avoid the compiler warning: > Variable 'ArrayObjects' is used before it has been assigned a value. A null > null reference exception could result at runtime. > Dim ArrayObjects() As AcadEntity The compiler is warning you that this variable /might/ have no value when you come to use it. Avoid this by giving the variable a value - even if that value just happens to be a /null/ one! Dim ArrayObjects As AcadEntity() = Nothing (I prefer the array braces with the Type, not the Variable - it just reads better, IMHO - has the same effect either way). OK, you /will/ still get a NullReferenceException later on if you don't give it another value, but it'll be your all own doing. :-) HTH, Phill W. |