Windows Forms

Re: How come I can call Public Methods of a Form as if they were Shared?

11-May-11 10:27

Luc Pattyn wrote:
If this is about VB6 or older

Nope, the code example I showed was VB.NET, Framework 4.0.

Luc Pattyn wrote:
In VB.NET, your code does not compile.

It compiles, runs great and works as expected (the Form is called with its Width set, the Buttons Text set etc.).

I just can't get over the fact that it goes against everything I have learned about encapsulation and that .NET is right there supporting it.

Luc Pattyn wrote:
You would need "Form1 implements Form", and then all methods/properties in DoSomethingElse() generate compile errors.

It gets worse....

Public Class Form1

	Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
		Form2.Something()
		Form2.Button1.Text = "Hello"
                Form2.Show()
	End Sub

        Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
		Form1.Show()
	End Sub

End Class

Public Class Form2

	Public Sub Something()
		Me.Text = "Test"
		Me.NothingIsSacredAnymore()
	End Sub

	Private Sub NothingIsSacredAnymore()
		MessageBox.Show("Hello")
	End Sub

End Class

I am starting Form1, which immediatly calls Form2.Something, without first instantiating it. Form2.Something calls a Private Sub and everything is ok. I can't call NothingIsSacredAnymore directly from Form1 though.
When I start the application I first get the MessageBox saying "Hello", then Form1 and Form2 show and Form2 has it's text set to "Test" and its Buttons Text set to "Hello".
When I click the Button1 on Form1 nothing happens if Form2 is already open. If it is not it opens Form2, but with default property settings.

It's an OO world.

Dave Kreskowiak11-May-11 10:56

Dave Kreskowiak

11-May-11 10:56

That's because, in order to make it easier to maintain some level of backwards compatibility with VB6 when converting projects from VB6 code to VB.NET, there is a little hidden collection of instances of all your Form classes in your app. If you look under My.Forms you'll find it.

I hate it. There's no way to completely get rid of it and doing so is a bad idea because it's also tied in with other Application Framework functionality.

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Re: How come I can call Public Methods of a Form as if they were Shared?

Sander Rossel11-May-11 11:09

Re: How come I can call Public Methods of a Form as if they were Shared?

11-May-11 11:09

Yet another reason to use C#.
Microsoft ignoring my encapsulation is a bitch... Frown | :(

It's an OO world.

Luc Pattyn11-May-11 12:41

Re: How come I can call Public Methods of a Form as if they were Shared?

11-May-11 12:41

Waw. Who would come up with "free forms"!

I had pasted the OP's code into an existing VB.NET project, and wasn't surprised it didn't compile at all, so I did not understand what the OP was on about...

Thumbs Up | :thumbsup:

Luc Pattyn [Forum Guidelines] [My Articles] Nil Volentibus Arduum

Please use <PRE> tags for code snippets, they preserve indentation, improve readability, and make me actually look at the code.

Eddy Vluggen11-May-11 10:44

Eddy Vluggen

11-May-11 10:44

Also works on older versions of VB.NET. There's a thread on StackOverflow[^] on the subject Smile | :)

I are Troll Suspicious | :suss:

Re: How come I can call Public Methods of a Form as if they were Shared?

Sander Rossel11-May-11 11:05

Re: How come I can call Public Methods of a Form as if they were Shared?

11-May-11 11:05

StackOverflower wrote:
VB6 programmers had a hard time with seeing the difference between a type and a reference to an object of that type. Form1 vs frm in your snippet. There's history for that, VB didn't get classes until VB4 while forms go all the way back to VB1. This is otherwise quite crippling to the programmer's mind

I spent about 30 minutes looking for some global variable today with no luck... Encapsulation is one of the most important aspects of Object Oriented Programming and Microsoft decides to NOT use it for Forms. I ask you, what is more crippling to the programmer's mind? Dead | X|

This sort of stuff leads to very unexpected behaviour in software... Microsoft should have dropped it in VB4 Unsure | :~

It's an OO world.

Eddy Vluggen11-May-11 11:34

Eddy Vluggen

11-May-11 11:34

Naerling wrote:
and Microsoft decides to NOT use it for Forms

After having read the reasoning on that thread, I can see why. Can't say I like it, just that I can see the reasoning. Just for fun, how about assigning null to a valuetype?

Naerling wrote:
Microsoft should have dropped it in VB4

Yes, I'm glad too that Microsoft introduced C# Smile | :)

I are Troll Suspicious | :suss:

Re: How come I can call Public Methods of a Form as if they were Shared?

MicroVirus30-May-11 4:55

MicroVirus

30-May-11 4:55

In what way is encapsulation broken? The only problem I can see with this is that if you wanted your constructor to be private then this would ruin it for you. Other than that, normal class access rules still apply.
VB.NET just acts like you declared Dim Form1 As New Form1. So the first call to a non-shared member of Form1 causes a new instance of Form1 to be created. But then, you wouldn't normally be calling non-shared members on the class anyway, so all in all the problem is fairly limited (that is to say: if you wrote your code without knowing this quirk, you wouldn't ever find out about it, because you wouldn't be directly accessing members through Form1 but via an instance).

That is not to say that I at all agree with this. I hated this quirk in VB6 already, as it was more confusing than anything. Completely unintuitive and destructive to the idea of classes and OOP for new programmers if they see this behaviour

Re: How come I can call Public Methods of a Form as if they were Shared?

CS140124-Jun-11 0:53

CS1401

24-Jun-11 0:53

its sounds good.. Confused | :confused:

Re: How come I can call Public Methods of a Form as if they were Shared?

Sander Rossel24-Jun-11 7:58

Only one Exe at an instance

24-Jun-11 7:58

How is ignoring encapsulation sounding good? Unsure | :~

It's an OO world.

pix_programmer23-Apr-11 6:19

pix_programmer

23-Apr-11 6:19

Hi!
I've developed an application using Windows Forms Managed C++. I've deployed it and installed at client systems. At present I can run many instances of my application at the same time. But I want only one at any particular instancde(ie. if I click the desktop short cut for my app,when already an instance is running, another instance of my app should not run). How to do this?

Re: Only one Exe at an instance

Luc Pattyn23-Apr-11 7:18

Re: Only one Exe at an instance

23-Apr-11 7:18

Have you searched[^] at all, you got the keywords right?

BTW: a second instance will run shortly, discover it isn't the first, possibly pass on the command line, then exit.

Smile | :)

Luc Pattyn [Forum Guidelines] [My Articles] Nil Volentibus Arduum

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Shameel26-Apr-11 2:00

Shameel

26-Apr-11 2:00

Technically speaking, you cannot prevent a second instance from coming up, but you can code your app in such a way that it detects if an instance is already running and pass on the command-line arguments and then exit. There are many approaches to this, one is to use a Mutex and the other is to use the System.Diagnostics.Process class to check if the process is already running.

How can i create a receipt(size 400*400) in crystal report C# 2.0 windows application [modified]

Member 436368017-Apr-11 20:14

Member 4363680

17-Apr-11 20:14

I need to print a receipt(size 400*400) in crystal report C# 2.0 windows application. i created the report,but its size can not change(Default Crystal Report page size).How can i reduce the page size to 400*400

I want to reduce the paper size in crystal report.when i am trying to reduce the paper size in printer setup, Paper size of all the reports that i am using in my project changes.But i need to chane the particular report...For that what to do.....

modified on Monday, April 18, 2011 2:22 AM

Re: How can i create a receipt(size 400*400) in crystal report C# 2.0 windows application

thatraja7-Jun-11 1:15

thatraja

7-Jun-11 1:15

For that you need to create custom paper size in your printer
HOW TO: Create a Custom Paper Size in Windows NT 4.0 using Access 2000[^]

How to customize papersize in crystal report?[^]

Here the answer for how to change paper size at runtime.
Crystal report page size @ run time[^]

thatraja

My Tip/Tricks
My Dad had a Heart Attack on this day so don't...

Windows 7 doest launch application on startup

Xmen Real 17-Apr-11 3:06

17-Apr-11 3:06

I've a C# application, sort of monitoring application which must run as Admin. So I added manifest file in that. I tried many ways to do, added in registry, added shortcut in Startup directory, added in Task Scheduler. But nothing seems to be working. Any idea ?

TVMU^P[[IGIOQHG^JSH`A#@`RFJ\c^JPL>;"[,*/|+&WLEZGc`AFXc!L
%^]*IRXD#@GKCQ`R\^SF_WcHbORY87֦ʻ6ϣN8ȤBcRAV\Z^&SU~%CSWQ@#2
W_AD`EPABIKRDFVS)EVLQK)JKQUFK[M`UKs*$GwU#QDXBER@CBN%
R0~53%eYrd8mt^7Z6]iTF+(EWfJ9zaK-iTV.C\y<pjxsg-b$f4ia>

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RobCroll17-Apr-11 4:46

RobCroll

17-Apr-11 4:46

And you have tried running the application logged on as Admin?
Any UI components?
Have you tried wrapping it as a service and installing as service?

"You get that on the big jobs."

Xmen Real 17-Apr-11 5:22

17-Apr-11 5:22

RobCroll wrote:
And you have tried running the application logged on as Admin?

yes didnt work, but I want it with every user

RobCroll wrote:
Any UI components?

RobCroll wrote:
Have you tried wrapping it as a service and installing as service?

cant, service has some restrictions Frown | :(

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Dave Kreskowiak17-Apr-11 5:37

Dave Kreskowiak

17-Apr-11 5:37

You cannot do this.

Every user is not going to have admin permissions ability. That means you cannot run the app as a normal user at all. Th eonly people who could run the app are those who are members of the Administrators group.

You have no choice but to run this as a service under a dedicated admin account.

What are you doing that requires admin priv's anyway?

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Dave Kreskowiak

Xmen Real 17-Apr-11 5:42

17-Apr-11 5:42

Dave Kreskowiak wrote:
What are you doing that requires admin priv's anyway?

-Update network IPs
-Take screenshot
-Socket Connection
-Shutdown/Restart PC

I don't know if any of above requires admin privilege but app doesnt work properly without it.

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Luc Pattyn17-Apr-11 6:07

17-Apr-11 6:07

Xmen W.K. wrote:
I don't know if any of above ...

with proper error handling and logging, you would know.

Hmmm | :|

Luc Pattyn [Forum Guidelines] [My Articles] Nil Volentibus Arduum

Please use <PRE> tags for code snippets, they preserve indentation, improve readability, and make me actually look at the code.

Xmen Real 17-Apr-11 6:12

17-Apr-11 6:12

it was written years ago and was working fine on xp, trying to save time by not going into source code.

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Luc Pattyn17-Apr-11 6:24

17-Apr-11 6:24

there is no excuse for not having proper error handling. not ever.

Unsure | :~

Luc Pattyn [Forum Guidelines] [My Articles] Nil Volentibus Arduum

Please use <PRE> tags for code snippets, they preserve indentation, improve readability, and make me actually look at the code.

Xmen Real 17-Apr-11 6:26

17-Apr-11 6:26

it is when the code is old and written by a newbie Smile | :)

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