VB.NET Forms App Architecture

Question

I'm a bit confused on exactly how the architecture for a VB.NET forms app actually works.

I've noticed in others' code, lines that read a little like this:

If frmMain.someBooleanProperty Then

but, I'm a bit confused because someBooleanProperty is then defined as an instance variable (i.e., as Public someBooleanProperty As Boolean in frmMain). How is it being referenced statically to access an instance variable? Is this just bad coding practice?

if `frmMain` is an instance of `Form18` then it is an instance object variable. if `frmMain` *is* the class name then a default instance is being used which is not usually a good idea — Ňɏssa Pøngjǣrdenlarp, Mar 04 '15 at 15:52
`frmMain` is defined as `Public Class frmMain`.... so shouldn't `frmMain` be a reference to that class? — Joseph Nields, Mar 04 '15 at 15:54
in that case, when it is used VB creates an instance which happens to have the same name - this is called the default instance and generally leads to trouble in various cases. — Ňɏssa Pøngjǣrdenlarp, Mar 04 '15 at 15:56
Sounds like a terribly flawed design.... But thanks for the explanation! — Joseph Nields, Mar 04 '15 at 15:57
It was added to VS2005 to be compatible with the way that VB6 worked. Its *not* a good idea but allows tinkers to get code running without having to understand OOP — Ňɏssa Pøngjǣrdenlarp, Mar 04 '15 at 15:58

score 0 · Accepted Answer · edited May 23 '17 at 12:15

0

For reasons of backwards compatibility, VB.NET automatically creates an instance of every Form. This instance is accessible through a global property which has the same name as the Form class itself.

More details can be found here:

Why is there a default instance of every form in VB.Net but not in C#?

edited May 23 '17 at 12:15

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answered Mar 04 '15 at 15:55

Heinzi

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VB.NET Forms App Architecture

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