MDI Form and only one instance of Child forms

[adalli]

Hi,

I have a MDI form with a menu structure. Each menu item opens a form using the following code.

Dim myForm As New frmClients
myForm.ShowDialog()
myForm = Nothing

The above code does not allow the user to go back to the MDI Menu unless he closes the current form. On the other hand if I use the code myForm.show, everytime the users goes to the menu, a new instance of the same form is opened.

Is there a way to open a new form when the form is not already displayed, and leaving the MDI Form available throughout but if an instance of a form is already opened, that instance would be displayed?

Thanks in advance,

 

[TipGiver]

Hi,

You can do:
Dim myForm As New frmClients
myForm.ShowDialog()
myForm = Nothing
<menuName>.enabled=false

And at closing of the form (event handler) do: <menuName>.enabled=true

I mean that you should disable the option to load a new form, and enable it back when the form is closed. This is a good way if you want to have only 1 instance of some mdiChild forms.

 

[ZmrAbdulla]

Here is another way..(tested on vb2005 express)

    Private WithEvents F2 As Form2

'==========================================
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        '  If the instance still exists... (ie. it's Not Nothing)
        If Not IsNothing(F2) Then
            '  and if it hasn't been disposed yet
            If Not F2.IsDisposed Then
                '  then it must already be instantiated - maybe it's
                '  minimized or hidden behind other forms ?
                F2.WindowState = FormWindowState.Normal  ' Optional
                F2.BringToFront()  '  Optional
            Else
                '  else it has already been disposed, so you can
                '  instantiate a new form and show it
                F2 = New Form2()
                F2.Show()
            End If
        Else
            '  else the form = nothing, so you can safely
            '  instantiate a new form and show it
            F2 = New Form2()
            F2.Show()
        End If

        If IsNothing(F2) Then MessageBox.Show("Is Nothing")
        If F2.IsDisposed Then MessageBox.Show("Is Disposed")


    End Sub

________________________________________________________
Zameer Abdulla
Help to find Missing people
Even a thief takes ten years to learn his trade.

 

[adalli]

That did it. Excellent, many thanks for your help.

 

[chrissie1]

of course you should try the OO way and make your class(form) a singleton. Not so hard and lots of examples o be found on google.

Christiaan Baes
Belgium

"Time for a new sig." - Me