Accessing the value of a control property on another page

[Marion]

I am just starting my first project in vb.net and trying to do something that
was very simple in vb6. In VB.net I have a form named fclsVehicles and on
the form is a listbox control named lstVehicles. I also have a standard module
named module1. From module1 I need to access the value of the lstVehicles
text property. With VB6 it was simple as form1.listbox1.text. I'm learning
now that you must use a public property and the Get Accessor. Can anyone
possible give my an example to get me started in the right direction. Anyone's
help would be very much appreciated. Thanks!

[Patrick Steele [MVP]]

In article <3c8e373b$1@10.1.10.29> (from Marion <myester1@yahoo.com>),
> I am just starting my first project in vb.net and trying to do something that
> was very simple in vb6. In VB.net I have a form named fclsVehicles and on
> the form is a listbox control named lstVehicles. I also have a standard module
> named module1. From module1 I need to access the value of the lstVehicles
> text property. With VB6 it was simple as form1.listbox1.text. I'm learning
> now that you must use a public property and the Get Accessor. Can anyone
> possible give my an example to get me started in the right direction. Anyone's
> help would be very much appreciated. Thanks!

On fclsVehicles:

Public ReadOnly Property VehText() As String
Get
Return listbox1.text
End Get
End Property

Assuming, of course, your listbox is named "listbox1".

--
Patrick Steele
Microsoft .NET MVP

[Marion]

Patrick Steele [MVP] <patrick@mvps.org> wrote:
>In article <3c8e373b$1@10.1.10.29> (from Marion <myester1@yahoo.com>),
>> I am just starting my first project in vb.net and trying to do something
that
>> was very simple in vb6. In VB.net I have a form named fclsVehicles and
on
>> the form is a listbox control named lstVehicles. I also have a standard
module
>> named module1. From module1 I need to access the value of the lstVehicles
>> text property. With VB6 it was simple as form1.listbox1.text. I'm learning
>> now that you must use a public property and the Get Accessor. Can anyone
>> possible give my an example to get me started in the right direction.
Anyone's
>> help would be very much appreciated. Thanks!
>
>On fclsVehicles:
>
>Public ReadOnly Property VehText() As String
> Get
> Return listbox1.text
> End Get
>End Property
>
>Assuming, of course, your listbox is named "listbox1".
>
>--
>Patrick Steele
>Microsoft .NET MVP

Patrick, I see how that works, thanks a lot. One more question. I have a
variable name strVehicleInfo in a standard module. I want to set strVehicleInfo
to the value of VehText. I know this may sound pretty simple, but is a little
intimidating trying to learn vb.net. Thanks!

[Patrick Steele [MVP]]

In article <3c8e6015$1@10.1.10.29> (from Marion <myester1@yahoo.com>),
> I have a
> variable name strVehicleInfo in a standard module. I want to set strVehicleInfo
> to the value of VehText. I know this may sound pretty simple, but is a little
> intimidating trying to learn vb.net. Thanks!

You'll need to use the variable that contains the instance of your form.
For example, assuming your form was created as "TheVehForm" then:

strVehicleInfo = TheVehForm.VehText

--
Patrick Steele
Microsoft .NET MVP

[Marion]

Patrick Steele [MVP] <patrick@mvps.org> wrote:
>In article <3c8e6015$1@10.1.10.29> (from Marion <myester1@yahoo.com>),
>> I have a
>> variable name strVehicleInfo in a standard module. I want to set strVehicleInfo
>> to the value of VehText. I know this may sound pretty simple, but is a
little
>> intimidating trying to learn vb.net. Thanks!
>
>You'll need to use the variable that contains the instance of your form.

>For example, assuming your form was created as "TheVehForm" then:
>
>strVehicleInfo = TheVehForm.VehText
>
>--
>Patrick Steele
>Microsoft .NET MVP

I tried that Patrick and I get a message that says "Reference to a non-shared
member requires an object reference." I apologize for being so ingnorant
about vb.net Can you suggest a good book to learn vb.net? Thanks!

[Patrick Steele [MVP]]

In article <3c8fbd59$1@10.1.10.29> (from Marion <myester1@yahoo.com>),
> >You'll need to use the variable that contains the instance of your form.
>
> >For example, assuming your form was created as "TheVehForm" then:
> >
> >strVehicleInfo = TheVehForm.VehText
> >
> >--
> >Patrick Steele
> >Microsoft .NET MVP
>
> I tried that Patrick and I get a message that says "Reference to a non-shared
> member requires an object reference." I apologize for being so ingnorant
> about vb.net Can you suggest a good book to learn vb.net? Thanks!

Try Dan Appleman's "Moving to VB.NET". It's pretty good.

Your problem is probably because you're accessing the form's name (it's
class name) instead of a created instance of that form (class). Here's
a quick example:

Public Class MyForm
Inherits System.Windows.Forms.Form

...
End Class

This defines a form (a class that inherits from the
System.Windows.Forms.Form class). To actually use this, you need to
create an instance of it. So, in a module:

Module Module1
Sub Main()
' define a variable of type 'MyForm'
Dim VehForm As MyForm

' create an instance of our form
VehForm = New MyForm()

' start a message processing loop
Application.Run(VehForm)
End Sub
End Module

If you simply try to access a member of the Class with:

MyForm.xxx

You'll get the error you described since MyForm is really a "template".
By creating an instance of it in 'VehForm', we have a usable object.

There's one exception to this rule of member access. A class can have
shared members. A shared member exists all the time -- you don't need
to create an instance of it to access the method. Here's an example:

Class MyUtilities
Public Shared Function AddAPeriod(ByVal str As String) As String
Return str & "."
End Function
End Class

This function can now be accessed simply by doing:

MyUtilities.AddAPeriod("hello")

Hope this gets you going!

--
Patrick Steele
Microsoft .NET MVP

[Marion]

>Thanks for the adice on the book Patrick. I will check it out at BooksAMillion
today. I am still having a problem so I will include the exact code I am
using. Within the GetVehicleInfo procedure in Module1 I am trying to do this,
strId = VehForm.VehText. Again, I really thank you for your time and expertise.
From a standard module:
Module Module1
Public p_conn As New ADODB.Connection()
Public strVehInfo As String
Public strVehYear As String

Sub Main()
Dim VehForm As fclsAutoTracker
VehForm = New fclsAutoTracker()
Application.Run(VehForm)
End Sub

Public Sub GetVehicleInfo()
Dim rstInfo As New ADODB.Recordset()
Dim strQuery As String
Dim strId As String
Dim VehForm As fclsAutoTracker
VehForm = New fclsAutoTracker()
strId = VehForm.VehText 'Patrick, This is where I am having the problem.


ConnectToDatabase()
'Mid(strVehInfo, 1, 1)
'strQuery = "Select * From VehicleInfo Where VehicleId = '" & strId
& "'"
'rstInfo.Open(strQuery, p_conn, ADODB.CursorTypeEnum.adOpenKeyset,
ADODB.LockTypeEnum.adLockReadOnly)
'strVehYear = rstInfo.Fields("Year").Value
'rstInfo.Close()
'p_conn.Close()
End Sub
Public Sub ConnectToDatabase()
p_conn.Open("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=f:\Program
Files\AutoMaint\AutoMaint.mdb")
End Sub
End Module

And this is my form:
Public Class fclsAutoTracker
Inherits System.Windows.Forms.Form
Public strText As String


Public ReadOnly Property VehText() As String
Get
Return lstVehicles.Text
End Get
End Property

Private Sub lstVehicles_SelectedIndexChanged(ByVal sender As System.Object,
ByVal e As System.EventArgs) Handles lstVehicles.SelectedIndexChanged
Select Case tabAutoTracker.SelectedIndex
Case 0 : GetVehicleInfo()
Case 1
Case 2
End Select
End Sub
End Class

[Patrick Steele [MVP]]

1. Change your GetVehicleInfo to accept a fclsAutoTracker object
(instead of defining one in the code):

Public Sub GetVehicleInfo(vForm as fclsAutoTracker)

2. Change the call to GetVehicleInfo to:

GetVehicleInfo(Me)

3. Finally, change the line of code with the error to:

vForm.VehText

The first change is to give GetVehicleInfo a variable which is the
instance of the form.

The next step is a modification to your form code that calls
GetVehicleInfo. You can use the keyword "Me" to pass the instance of
the object you're running inside (the VehForm).

Finally, the GetVehicleInfo gets the string from the form passed in.

However, to better separate the logic in this app, GetVehicleInfo really
just needs the ID. Instead of passing it a form from which you pull the
ID, you could simply pass the ID itself:

Public Sub GetVehicleInfo(strId as String)

Now the GetVehicleInfo is more resusable since it's not tied to
requiring a fclsAutoTracker class.

--
Patrick Steele
Microsoft .NET MVP

[Marion]

Patrick Steele [MVP] <patrick@mvps.org> wrote:
>
>1. Change your GetVehicleInfo to accept a fclsAutoTracker object
>(instead of defining one in the code):
>
> Public Sub GetVehicleInfo(vForm as fclsAutoTracker)
>
>2. Change the call to GetVehicleInfo to:
>
> GetVehicleInfo(Me)
>
>3. Finally, change the line of code with the error to:
>
> vForm.VehText
>
>The first change is to give GetVehicleInfo a variable which is the
>instance of the form.
>
>The next step is a modification to your form code that calls
>GetVehicleInfo. You can use the keyword "Me" to pass the instance of
>the object you're running inside (the VehForm).
>
>Finally, the GetVehicleInfo gets the string from the form passed in.
>
>However, to better separate the logic in this app, GetVehicleInfo really

>just needs the ID. Instead of passing it a form from which you pull the

>ID, you could simply pass the ID itself:
>
>Public Sub GetVehicleInfo(strId as String)
>
>Now the GetVehicleInfo is more resusable since it's not tied to
>requiring a fclsAutoTracker class.
>
>--
>Patrick Steele
>Microsoft .NET MVP

Patrick, I made the changes you suggested and now I am getting:

Argument not specified for parameter 'vForm' of 'Public Sub GetVehicleInfo(vForm
As fclsAutoTracker)'.

I will continue to look at this and try to figure it out. It's like learning
to walk all over again! Thanks for all of your help.

[Patrick Steele [MVP]]

In article <3c911ae0$1@10.1.10.29> (from Marion <myester1@yahoo.com>),
> Patrick, I made the changes you suggested and now I am getting:
>
> Argument not specified for parameter 'vForm' of 'Public Sub GetVehicleInfo(vForm
> As fclsAutoTracker)'.

Are you sure you're changing the call to GetVehicleInfo to include the
'Me' reference? I.e.:

GetVehicleInfo(Me)

--
Patrick Steele
Microsoft .NET MVP