Reuse class to multiple forms

P

PetCar

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Nov 30, 2003
Messages
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How do i reuse a class from withing two diffrent forms?

clsCommon is to be used with both frmMain and frmSettings, but when starting the second form (frmSettings) i get "Specified cast is not valid".

The code i use is:

Code: 
#clsCommon
Public Class clsCommon

    Private objForm As frmMain

    Public Sub New(ByVal objCallingForm As Form)
        objForm = objCallingForm
    End Sub

    Public Sub DoSomething()
        objForm.change_form_in_some_way
    End Sub

End Class

#frmMain
Public Class frmMain

    Inherits System.Windows.Forms.Form
    Private clsCommon As New clsCommon(Me)

    Private Sub Button4_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button4.Click
        Dim frmSettings As New frmSettings
        frmSettings.Show()
    End Sub

End Class

#frmSettings
Public Class frmSettings

    Inherits System.Windows.Forms.Form
    Private clsCommon As New clsCommon(Me)

    Private Sub frmSettings_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        clsCommon.ShowUserMessage(0, , "Hej hej", True, False)
    End Sub

End Class

When clicking button4 to show the frmSettings i get the error "Specified cast is not valid".

I know that there is some error in clsCommon:
Code: 
Private objForm As frmMain
But how can i do this different?

Im so into the old VB6 that my mind is twisted.. :(

Thanks!

// Peter
 
you should be using objCallingForm As frmMain , not as Form , eg:
Code: 
#clsCommon
Public Class clsCommon

    Private objForm As frmMain

    Public Sub New(ByVal objCallingForm As frmMain) /// not As Form
        objForm = objCallingForm
    End Sub

    Public Sub DoSomething()
        objForm.change_form_in_some_way
    End Sub

End Class
 
if its a Class and Not a form , you shouldnt do it like above , the above is a way of creating reference to a form , eg:
Code: 
Public Class Form2
    Inherits System.Windows.Forms.Form

#Region " Windows Form Designer generated code "

    Public frmMe As Form2

    Public Sub New(ByVal f2 As Form2)
        MyBase.New()
        frmMe = f2

Code: 
Public Class Form3
    Inherits System.Windows.Forms.Form

#Region " Windows Form Designer generated code "

    Public frmMe1 As Form3

    Public Sub New(ByVal f3 As Form3)
        MyBase.New()
        frmMe1 = f3

in frmMain ...
Code: 
Dim frmSecond As New Form2(Me)
Dim frmThird As New Form3(Me)
/// do stuff
 
Well, i got two forms that i want to use the same class to call common functions. I got it to work as i wanted. Thanks!

What i did in my real project was attaching a notfyicon on the frmMain, and i wanted to get to that via the class. But now i realize i must do this the other way around.

What is the best way to create an application that need to access this notifyicon from all classes and forms?

Shall i start the project from a class (Sub Main) and then start all forms from there. As it is right now i use frmMain as startup object.

Feedback?

// Peter
 
the penny dropped after , lol
Code: 
[color=green]/// the class / form you wish to access from both forms ...[/color]
[Color=Blue]Public Class[/color] Form3
    [Color=Blue]Inherits[/color] System.Windows.Forms.Form

#[color=blue]Region[/color] [color=gray]" Windows Form Designer generated code "[/color]

    [Color=Blue]Private[/color] frm1 [Color=Blue]As[/color] Form1
    [Color=Blue]Private[/color] frm2 [Color=Blue]As[/color] Form2

    [Color=Blue]Public Sub[/color] [Color=Blue]New[/color]([Color=Blue]Optional[/color] [Color=Blue]ByVal[/color] f1 [Color=Blue]As[/color] Form1 = [Color=Blue]Nothing[/color], [Color=Blue]Optional[/color] [Color=Blue]ByVal[/color] f2 [Color=Blue]As[/color] Form2 = [Color=Blue]Nothing[/color])
        [Color=Blue]MyBase[/color].New()
        [Color=Blue]If[/color] [Color=Blue]Not[/color] f1 [Color=Blue]Is[/color] [Color=Blue]Nothing[/color] [Color=Blue]AndAlso[/color] [Color=Blue]Not[/color] f2 [Color=Blue]Is[/color] [Color=Blue]Nothing[/color] [Color=Blue]Then
[/color]            frm1 = f1
            frm2 = f2
        [Color=Blue]ElseIf[/color] [Color=Blue]Not[/color] f1 [Color=Blue]Is[/color] [Color=Blue]Nothing[/color] [Color=Blue]Then
[/color]            frm1 = f1
        [Color=Blue]ElseIf[/color] [Color=Blue]Not[/color] f2 [Color=Blue]Is[/color] [Color=Blue]Nothing[/color] [Color=Blue]Then
[/color]            frm2 = f2
        [Color=Blue]End[/color] [Color=Blue]If

[/color]        [Color=Green]This[/color] [Color=Green]call is required by the Windows Form Designer .[/color]
        InitializeComponent()

        [Color=Green]Add any initialization after the InitializeComponent() call[/color]

    [Color=Blue]End Sub[/color] 
[color=green]/// test it with a button click ...[/color]
[Color=Blue]Private Sub[/color] Button1_Click([Color=Blue]ByVal[/color] sender [Color=Blue]As[/color] System.Object, [Color=Blue]ByVal[/color] e [Color=Blue]As[/color] System.EventArgs) [Color=Blue]Handles[/color] Button1.Click
        [Color=Blue]If[/color] [Color=Blue]Not[/color] frm1 [Color=Blue]Is[/color] [Color=Blue]Nothing[/color] [Color=Blue]Then[/color]
           frm1.Button1.PerformClick()
        [Color=Blue]End If[/color]
    [Color=Blue]End Sub[/color]
from one of your forms , eg: Form1 ...
Code: 
    [Color=Blue]Private[/color] [Color=Blue]Sub[/color] Form1_Load([Color=Blue]ByVal[/color] sender [Color=Blue]As[/color] System.Object, [Color=Blue]ByVal[/color] e [Color=Blue]As[/color] System.EventArgs) [Color=Blue]Handles[/color] [Color=Blue]MyBase[/color].Load
        [Color=Blue]Dim[/color] frm [Color=Blue]As[/color] [Color=Blue]New[/color] Form3([Color=Blue]Me[/color])
        frm.Show()
    [Color=Blue]End[/color] [Color=Blue]Sub

[/color]    [Color=Blue]Private[/color] [Color=Blue]Sub[/color] Button1_Click([Color=Blue]ByVal[/color] sender [Color=Blue]As[/color] System.Object, [Color=Blue]ByVal[/color] e [Color=Blue]As[/color] System.EventArgs) [Color=Blue]Handles[/color] Button1.Click
        [COLOR=Green]/// you will call this from Form3 to test you have access to this Form.[/COLOR]
        MessageBox.Show("test")
    [Color=Blue]End[/color] [Color=Blue]Sub[/color]
 
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