VB 10 thoughts (part 3)

re: VB 10 thoughts (part 3)

bill — Fri, 12 Oct 2007 00:50:17 GMT

Hi Paul,

The problem with DefaultValue attribute is if you pass it an enum it compiles using the DefaultValue(Integer) constructor. As such winforms doesn’t recognize the default value *properly*. The bug is more o nthe winforms side of things, but being able to CObj in the attribute would address this; that is the language features would let us work around bugs in frameworks <g>.

Here's some sample code :

Public Class UserControl1

Private m_FooProp As Foo = Foo.Baz

<System.ComponentModel.DefaultValue(Foo.Baz)> _

Public Property FooProp() As Foo

Get

Return m_FooProp

End Get

Set(ByVal value As Foo)

m_FooProp = value

End Set

End Property

End Class

Public Enum Foo

Bar

Baz

End Enum

Note that when you reset the value on the winforms designer the value is still written in the initialize component section. To get it to work correctly you need to use this overload:

<System.ComponentModel.DefaultValue(GetType(Foo), "1")> _

Note how the integer value had to be presented as a string. In C# the original code works because they compile it to DefaultValue(Object) instead of DefaultValue(Integer)

re: VB 10 thoughts (part 3)

Paul Vick — Fri, 12 Oct 2007 00:14:54 GMT

On #13, we still don't allow CObj, but I believe we did fix the enum problem (I think it had to do with weird overloading rules and conversions). The following code compiles fine:

Enum Foo

Bar

End Enum

<System.ComponentModel.DefaultValue(Foo.Bar)> _

Class Baz

End Class

Are there other cases?

re: VB 10 thoughts (part 3)

bill — Tue, 09 Oct 2007 00:03:08 GMT

Jonathan, they aren't necessarily instance variables. If you use Static in a Shared method it is Shared across all instances. So the lifetime (instance versus non instance) is controlled by the surrounding block.

But back to the main issue: people do find "static" confusing. The only sense of the terminology is to mean the same as Shared does in VB. As Bob put it, the variable is persistant. That is it is "Shared". If the method is an instance method the variable is shared amongst all calls to the method from that instance; if the method is Shared, then the variable is Shared amongst all calls to that method from all instances.

re: VB 10 thoughts (part 3)

Bob Bingham — Mon, 08 Oct 2007 17:41:38 GMT

How about "Persistant"? Or is that Persistent? Oh well, the IDE will type it out for us bad spellers. ;)

re: VB 10 thoughts (part 3)

Jonathan Allen — Mon, 08 Oct 2007 04:16:23 GMT

I have to disagree with you on item 3. I think "Shared" would be misleading because they are instance variables, not class-wide variables.