[VB.NET] How to reference object from Panel

[JK1150]

I have too panels in my program, one of them has a list on it, and I want to reference the list from the other panel. To be more specific, my list is printersList in panel goPanel, and I want panel goPanel to reference it. I get the the error: "Reference to a non-shared member requires an object reference." I've done a lot of research on this error, for about the past hour, but have not been able to make sense out of it, can anyone point me in the right direction?

Thanks

[Winston]

lol can you do a screenshot and highlight wat u want to achieve.

[JK1150]

Not sure how I could show it in a screenshot, but basically:

- I have 2 user control forms, startPanel and goPanel

- I have a check list box (printersList) on startPanel, that I want to reference on goPanel, so I can list the things checked in the check box.

- When I try to do startPanel.printersList.CheckedItems, it says "Reference to a non-shared member requires an object reference."

[Winston]

so you have two panels.

and a Checked ListBox

the Checked ListBox resides in one of those panels. You're trying to access this Checked ListBox.

Have you tried just doing printersList.CheckedItem

[JK1150]

yea, I get "printersList is not declared"

documentation I read says I have to reference it as an object, but I'm not sure how to go about that with a list.

[Winston]

lol, this task is simple, i dunno what ur doing wrong, perhaps u can post the solution or u can PM me and email me it and i can have a look at it.

[JK1150]

not sure what i'm doing wrong. i just need to reference an object from Class goPanel in Class startPanel, but I can't get it working.

[Winston]

lol you're either not explaining well enough or ur using terms incorrectly, u need to show us the solution or we cant help u.

[JK1150]

Not sure how else I can explain it. Basically, I have a list in one user control, and want to access it in another user control window. How would one generically go about doing this?

[Winston]

ok edit, i think uve been confusing me all along, firs u said panels, and now u said user controls, so what is it?

[John Veteran]

I think you have to loop through the controls in the panel, finding one of the right type (cast it as the type of control you're looking for) and then reference it that way.

That or provide a public accessor in the form that returns the control.

[JK1150]

Winston, it is a user control that is reference by a panel, so the short answer would be that it's a user control.

John, how would I go about doing that? That is what MSDN has said, but I can't get it working.

This is what MSDN says for the error I am getting:

  Quote

You have referenced a non-shared member within your code and failed to supply an object reference. You cannot use the class name itself to qualify a member that is not shared. The instance must first be declared as an object variable and then referenced by the variable name.

Error ID: BC30469

To correct this error

Declare the instance as an object variable.

Reference the instance by the variable name.

I'm not sure how to do this, can someone describe generally how I would set this up?

[mlynch]

you have to declare the list as public or friend, if u just dragged and dropped it on the form is going to be declared private and not accessible by by any other object than the one that instanciated it. Thats why you get a bad reference. John proposed an even better idea (and the correct OO way) of providing a public property or method to access the control while still keeping the control private.

[JK1150]

yea, that's what MSDN said to do (John's way), not sure how to go about that though. The checkedlistbox's name is printersList in user control startPanel, so when I try Dim printersList2 As CheckedListBox, and set printersList2 = startPanel.printersList, that doesn't work. Am I going about this wrong?

Edited March 8, 2006 by JK1150

[mlynch]

ok scratch what I said up there, new objects are declared as friends. If these are all panels on the same form you should be able to loop through. Can you give a more specific example of that you are trying to do? do you want to show the same list twice? or are you using the values from printerslist to modify another list on the form? also is this winform or webform? aslo can you post a screenie of what you are trying to do (just disable the reference line of code). Visuals help demonstrate your desired behavior

[JK1150]

i'm not sure what i could take a screenshot of, but I have a mainFrame (Windows App) with a panel in it. The program starts by loading a user control into the Panel, which includes printersList, a list of printers on a network that can be installed. The user will click start, which will change the panel to the user control goPanel with a progress bar, cancel button, etc., which will use what was checked on the checked list in startPanel to install the selected printers. This is a winform. Is there a specific part of this you want to see?

[JK1150]

I guess the best way to describe it is "how do I reference a CheckedListBox that is in one class from another class."

[nowimnothing]

It sounds to me like you need to have your user control expose the checked list box as a public property. That way other user controls have access to it.

In your code for your goPanel control, you'd have something like this (this is C#, hopefully you can translate it if you need to)

class MyGoPanelControl : UserControl

{

// Next line probably added by your designer automatically

private CheckedListBox printersList;

public CheckedListBox PrintersList

{

get { return printersList; }

}

}

then, anything that can access an instance of MyGoPanelControl, can access the printersList control inside of it via the property.

Is that what you were looking for?

[JK1150]

I don't think you can return a checkedlistbox in visual basic, that is the basic idea of what needs to be done though, I am just new to VB and am not sure how to get it done.

Edited March 8, 2006 by JK1150

[nowimnothing]

I would be very surprised if you could not returna checkedlistbox in visual basic .net. Its just a class like anything else. It just happens to also have a visual representation.

I ran my code through a converter to get it to VB.NET:

Class MyGoPanelControl

Inherits UserControl

' Next line probably added by your designer automatically

Private printersList As CheckedListBox

Public ReadOnly Property PrintersList() As CheckedListBox

Get

Return printersList

End Get

End Property

End Class

[JK1150]

Thanks for your help, but this didn't compile in visual basic 2005, I believe because get is a file i/o property

[Winston]

Ok, i added a new user control, added a panel into the user control, dropped a checkedlistbox into the panel.

Now i added the new user control to my form, and added a button which adds new items to the checkedlistbox.

Check out the attachment to see if that's what you're after.

[JK1150]

If you put that button on another user control rather than in the main frame, that is basically what I need to know how to do.

(I have the users select printers from a list, click go, and then a progress screen will come up where the "goPanel" class will need to know which printers the user selected in the "startPanel" class)

Thanks for all your help so far, VB.NET certainly is an interesting learning experience.

Edited March 9, 2006 by JK1150

[Winston]

ok here it is.

You need to look at the form designer code, i had to invoke a diffferent constructor for the useercontrol2

[JK1150]

where did you invoke the different constructor?

OK, thanks for all your help, I got it. I really appreciate the effort you went through to help me get this working. Thanks again.

[Winston]

I invoked the parameterized constructor in the form designer code.

That's where the Usercontrol gets created, that user control needs to get a reference of the checkedlistbox that's all

I'm glad you've finally got it working.