[RESOLVED] Setting object(Form) to nothing from within the object

[GremlinSA]

Well during testing the project came up with an interesting bug, If we close the form object (and dispose of it), it's object has not been set to Nothing, and now still responds to events..

Creating the Form ....

        Private WithEvents FormVending As FrmVending

        Private Sub MenuItemOnClick_Vend_CredRef(ByVal sender As Object, ByVal e As EventArgs)
            FormVending = New FrmVending(thisUserID, thisUserName)
            FormVending.MdiParent = Me
            FormVending.Show()
        End Sub

When the form is loaded it must get data from the comms object, everytime a token is inserted.. Like this..

        Private Sub Comms_Mode_Token_In() Handles Comms_Mode.Token_In
            ToolStripReaderStatus.Text = "[Token IN]"
                    If Not FormVending Is Nothing Then
                        FormVending.TokenData = Comms_Mode.TokenData
                    End If
        End Sub

However when the form is closed, it is still replying to the above code.. even though i am disposing of it..

        Private Sub FrmVending_FormClosed(ByVal sender As Object, ByVal e As System.Windows.Forms.FormClosedEventArgs) Handles Me.FormClosed
            Me.DestroyHandle()
            Me.Dispose(True)
        End Sub

The thing is, I probably can simply add an event to the form so that the main class will set the object reference to Nothing. But i'm looking for a solution where i can set the object to nothing from with in the object, as i may have to add this to several other forms (many of which currently have not been setup for events..) ..

Thanks

Gremmy...

[javajawa]

I'd personally solve the problem by doing it the other way round:

Private WithEvents mfDialog as frmDialog

Private Sub mfDialog_frmClosed(...) Handles ...
  mfDialog = Nothing
End Sub

Then you can also use the frmClosing event to trap responses to data.

Doesn't really answer your question, but it's always seemed to work for me...

[HanneSThEGreaT]

This looks like your "parent" form and FormVending's code are in one module because of WithEvents.

Look closely at your FrmVending_FormClosed event. You will notice, that it still Handles Me.FormClosed

It should be :

 Private Sub FrmVending_FormClosed(ByVal sender As Object, ByVal e As System.Windows.Forms.FormClosedEventArgs) Handles FormVending.FormClosed
        FormVending.Dispose()
        FormVending = Nothing
    End Sub

I don't know if you have noticed, but if you had set a break point inside your FormClosed event, it would not have entered Break mode once you have closed FormVending, but only once you have closed the "parent" form.


I did a small test, that looked like this :

Public Class Form1
    Private WithEvents FormVending As New Form2
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        FormVending.Show()

    End Sub

    Private Sub FrmVending_FormClosed(ByVal sender As Object, ByVal e As System.Windows.Forms.FormClosedEventArgs) Handles FormVending.FormClosed
        FormVending.Dispose()
        FormVending = Nothing
    End Sub

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        If Not FormVending Is Nothing Then
            MessageBox.Show("Not Nothing")
        Else
            MessageBox.Show("Nothing")
        End If
    End Sub
End Class

And it gave me the correct results.

I hope my post was useful boet!

[GremlinSA]

Thanks guy's you put me on the right path...

This code was in the form class (and not the main class), and thats why it handles Me.formclosed..

        Private Sub FrmVending_FormClosed(ByVal sender As Object, ByVal e As System.Windows.Forms.FormClosedEventArgs) Handles Me.FormClosed
            Me.DestroyHandle()
            Me.Dispose(True)
        End Sub

However i killed that sub and put it in the Main Form..

        Private Sub FormVending_FormClosed(ByVal sender As Object, ByVal e As System.Windows.Forms.FormClosedEventArgs) Handles FormVending.FormClosed
            FormVending.Dispose()
            FormVending = Nothing
        End Sub

Everything is working correctlly... Now i need to go through all 40 Forms and add the same in..

I was hoping there was something along the lines of Me = nothing, so that i could clear each form within it's own class, and not the owner class..

Well the problem is solved Thanks Guys...

[javajawa]

You might be able to generalise it using AddHandler, and testing the sender object against all of the forms you have defined...but that might get more tricky...

[GremlinSA]

I'd personally solve the problem by doing it the other way round:

Then you can also use the frmClosing event to trap responses to data.

I normally use the Forms internal Formclosing event to check if the form may close or if an edit is still in progress..

        Private Sub FrmSpecialTokens_FormClosing(ByVal sender As Object, ByVal e As System.Windows.Forms.FormClosingEventArgs) Handles Me.FormClosing
            If _Close Then e.Cancel = True
        End Sub

If and edit is in progress or any other reason to prevent the form from closing you set _Close to True ... To allow the form to close set it to False.. this even overides the "X" button on the form...

Gremmy...