VB. NET Shared Sub Main()

[Guest]

HI,

I’m learning C# and already know VB .Net. I noticed that C# you have a
Static Void Main () (entry point of the app).

Well that got me thinking, I was told that VB.net removed “The Black Boxâ€
of software (hidden code). Where is my Shared sub Main ()? When I create a
blank app and run it, it asked me where is Shared sub Main. So, can I assume
that it’s hidden on a win32 app? And if so, why hide it?



Thanks

 

[Cor Ligthert]

Hi Andre,

Sub Main is an standard part of dotNet.

When it is ommitted as with VBNet in the standard way than that one is taken
in the Form you choose as startup in the properties of your application. It
is not a win32 part.

It is not hidden, you just do not have to use it, however when you want,
feel free to add that class a lot of VBNet programmers are using that as I
have seen.

Cor

 

[Philip Rieck]

What cor states below isn't exactly correct, or at least, isn't worded
exactly correct. Every .net application requires a managed entry point. (a
"shared sub main")

However, in a windows form application the vb.net compiler will
automatically create one for you if you chose a startup form. If you choose
a form named "Form1", the code it creates is :
<STAThread> _
Public Shared Sub Main()
Application.Run(New Form1)
End Sub

Note that this code is included in your application assembly, currently
pushed into the "Form1" type. So it's as if you had typed that exact code
above into your Form1 class and set Form1.Main as your startup method.

So no, it's not really hidden, it's just conveniently created for you if you
don't write it yourself. I personally write it myself when creating VB.net
winforms apps - it removes any ambiguity when looking at the code (you don't
have to check the project properties to figure out where the app starts),
and I can easily customize the startup code.


-Philip Rieck
http://philiprieck.com/blog/

 

[Gerry O'Brien [MVP]]

Just to add what Cor has posted, VB also has a weird quirk whereby if you
create an app, then go into the code module for the Class Form1 and change
the name to something other than Form1, you must then also go into the
project properties and tell if to use the new class name for the form as the
startup form. It assumes that it is still looking for Form1 and can no
longer find that class.

If you do not do this, you will get the error that Sub Main cannot be found.

 

[Guest]

Thanks All, I wish VB.net was alittle more like C# where the code is there
for you. Maybe have a check box to show or hide the code for those that don't
want to see it.

André

 

[Guest]

Does this show up in the code? I can't seem to find it. If I wanted to
write my own main to start the form, where would I put it? Just before the
class name?

 

[Philip Rieck]

It doesn't show up in the code - it is injected at compile time, so it
*does* show up in the compiled IL.

If you wanted to do it yourself, you can
1) Create a module and add a "Sub Main" to it

2) Create a class file called something like "Startup.vb" and put this in
it:
Public Class Startup
<STAThread()> _
Public Shared Sub Main()
Application.Run(new Form1)
End Sub
End Class

3) put it in your existing Form1 class (inside the class)
....
Public Class Form1
Inherits System.Windows.Forms.Form

...
<STAThread()> _
Public Shared Sub Main()
Application.Run(new Form1)
End Sub
...
End Class



It doesn't really matter what class it's in, as it's a static (Shared)
method. All you need to do is make sure that it has access to the types and
members you want (Form1 is it in this case). I prefer putting it in a
Startup.cs in c#, or a module in vb.net, but I'm sure not everyone would
agree with me.

 

[Chris Dunaway]

So no, it's not really hidden, it's just conveniently created for you if you
don't write it yourself. I personally write it myself when creating VB.net

Since you cannot see it, then by definition, it is hidden. The OP was just
making the observation that VB.Net was supposed to have eliminated that
type of "Black Box" functionality. Yet it still exists.

--
Chris

dunawayc[AT]sbcglobal_lunchmeat_[DOT]net

To send me an E-mail, remove the "[", "]", underscores ,lunchmeat, and
replace certain words in my E-Mail address.

 

[Cor Ligthert]

Andre

Thanks All, I wish VB.net was alittle more like C# where the code is
there
for you. Maybe have a check box to show or hide the code for those that
don't
want to see it.

In VBNet is as well all the code for you, the only thing is that there is in
this case used a feature of the .Net framework what is not done in C#.

In C# you cannot use it, in VBNet you are free to use it.

Cor

 

[Herfried K. Wagner [MVP]]

Just to add what Cor has posted, VB also has a weird quirk whereby if you
create an app, then go into the code module for the Class Form1 and change
the name to something other than Form1, you must then also go into the
project properties and tell if to use the new class name for the form as
the startup form. It assumes that it is still looking for Form1 and can
no longer find that class.

If you do not do this, you will get the error that Sub Main cannot be
found.

ACK, but VS.NET will kindly show a dialog that allows picking the new
startup object .

 

[Jay B. Harlow [MVP - Outlook]]

Chris,
Realistically do you think there is any high-level language that does not
have certain "black box" features?

As others have mentioned you can use ILDASM to see the actual
implementation.

Look at how Events & Properties are implemented in both VB.NET & C#.

Look at how SyncLock is implemented
Look at how For Each is implemented

Look at how a number of other language constructs are implemented...

IMHO if you truly want to avoid the "black box" you would need to be coding
in assembler or even straight machine code. Note I consider IL & the CLR a
black box also, as it isolates me from the machine itself...

IMHO the "black box" that .NET eliminates is the designer code that was used
to create the form itself. As now it is all VB.NET code in the "Windows Form
Designer generated code" region of your form.

Just a thought
Jay

So no, it's not really hidden, it's just conveniently created for you if
you
don't write it yourself. I personally write it myself when creating
VB.net

Since you cannot see it, then by definition, it is hidden. The OP was
just
making the observation that VB.Net was supposed to have eliminated that
type of "Black Box" functionality. Yet it still exists.

--
Chris

dunawayc[AT]sbcglobal_lunchmeat_[DOT]net

To send me an E-mail, remove the "[", "]", underscores ,lunchmeat, and
replace certain words in my E-Mail address.

 

[Guest]

Thanks Philip for a VERY clear explaination.

It doesn't show up in the code - it is injected at compile time, so it
*does* show up in the compiled IL.

If you wanted to do it yourself, you can
1) Create a module and add a "Sub Main" to it

2) Create a class file called something like "Startup.vb" and put this in
it:
Public Class Startup
<STAThread()> _
Public Shared Sub Main()
Application.Run(new Form1)
End Sub
End Class

3) put it in your existing Form1 class (inside the class)
....
Public Class Form1
Inherits System.Windows.Forms.Form

...
<STAThread()> _
Public Shared Sub Main()
Application.Run(new Form1)
End Sub
...
End Class



It doesn't really matter what class it's in, as it's a static (Shared)
method. All you need to do is make sure that it has access to the types and
members you want (Form1 is it in this case). I prefer putting it in a
Startup.cs in c#, or a module in vb.net, but I'm sure not everyone would
agree with me.

--
-Philip Rieck
http://philiprieck.com/blog/

-

 

[Jon Skeet [C# MVP]]

In VBNet is as well all the code for you, the only thing is that there is in
this case used a feature of the .Net framework what is not done in C#.

In C# you cannot use it, in VBNet you are free to use it.

Which framework feature are you talking about, Cor? I'm not doubting
you - just trying to work out exactly what you mean.

 

[Cor Ligthert]

Jon,

I have it from a book, which I have not in my possesion now.

I do not like to argue about it now, (not that I do not believe it is true,
however I am not completly sure on which level it is, build on top or build
as feature in some classes, I know that it works with WindowForms, Webforms,
Webservices and a self build Sub Main object so probably it is not a build
in feature in some classes however in a higher level).

I cannot find at the moment the same information I readed on MSDN.

However this will still cover in my opinion my last answer.

http://msdn.microsoft.com/library/d...vsintro7/html/vxurfstartupobjectdialogbox.asp

I hope this gives some idea's

Cor

 

[Jon Skeet [C# MVP]]

I have it from a book, which I have not in my possesion now.

I do not like to argue about it now, (not that I do not believe it is true,
however I am not completly sure on which level it is, build on top or build
as feature in some classes, I know that it works with WindowForms, Webforms,
Webservices and a self build Sub Main object so probably it is not a build
in feature in some classes however in a higher level).

I cannot find at the moment the same information I readed on MSDN.

However this will still cover in my opinion my last answer.

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vsin
tro7/html/vxurfstartupobjectdialogbox.asp

I hope this gives some idea's

If you're talking about VB.NET projects not needing to have an explicit
Main method in code, then I believe it's just the VB.NET compiler
putting one in for you if you tell it which type to use and if that
type inherits from Form.

Here's a nice small sample:

-------- Test.vb ----------
Option Strict On

Public Class Test
Inherits System.Windows.Forms.Form
End Class
---------------------------

Compile with:
vbc /r:System.dll,System.Windows.Forms.dll /main:Test Test.vb

Then look at the result - an exe with a perfectly normal Main method in
the Test type.

In other words, this isn't a framework feature which C# can't use, it's
a VB.NET compiler feature (and not one I personally like, but that's a
different matter).

 

[Cor Ligthert]

"Jon Skeet>

In other words, this isn't a framework feature which C# can't use, it's
a VB.NET compiler feature (and not one I personally like, but that's a
different matter).

I said I am now not in the possition of the book where I thought that I had
readed it in, therefore I have no start point for furter investigation and
did even not want to go for idalsm what I could have done before, however
than still does not misprove what I thought I have readed.

That you personally not like this feature in VBNet is your personally
decission as you wrote.

The Sub Main is even from before the C time as a needed hard named
startpoint (address 0). I never liked it that it was not variable.

To like this, sounds for me very conservative, while I like innovation.

Cor