MDI Child form calling, not generation.

Question

Hello.

I have an MDI form with 3 nested children with in it. As of right now all it can do is display a new form. For example: each time I press the menu button, the new child form(Form1) is created. Now, if I press that same menu button a second or subsequent time a new Form1 is created and it appears over the previous one.

What I would like is that each time the event handler is triggered (a menu item_click on the parent form) that instead of a completely "new" child form being produced(a new window popping up) it would instead pull up the appropriate child form that is attached to the trigger.

I suppose it would be something like reusing an object.

Any help would be greatly appreciated.

Here's the code sample I'm using:

Private Sub RadMenuItem1_Click(ByVal sender As System.Object, ByVal e As_
System.EventArgs) Handles RadMenuItem1.Click 
Dim NewMDIChild As New InventoryForm1()
'Set the Parent Form of the Child window.'
NewMDIChild.MdiParent = Me
'Display the new form.'
NewMDIChild.Show()

Answer 1

Try the following (note that I haven't done VB .Net in a while, so the syntax may be off)

Dim ChildInstances As New Dictionary(Of RadMenuItem, Form)

Private Sub RadMenuItem1_Click(ByVal sender As Object, ByVal e As EventArgs) Handles RadMenuItem1.Click 
    Dim ChildForm As Form

    If Not ChildInstances.TryGetValue(RadMenuItem1, Out ChildForm) Then
        Set ChildForm = New InventoryForm1()
        ChildForm.MdiParent = Me
        ChildInstances.Add(RadMenuItem1, ChildForm)
    Else If ChildForm.Disposed Or Not ChildForm.Visible Then 'The user closed the form
        Set ChildForm = New InventoryForm1()
        ChildForm.MdiParent = Me
        ChildInstances(RadMenuItem1) = ChildForm
    End If

    ChildForm.Show()
End Sub

Answer 2

I think what you want here is a class level variable for the form. Something like -

'Class level (outside of a method)
Dim NewMDIChild As InventoryForm1

Private Sub RadMenuItem1_Click(ByVal sender As Object, ByVal e As EventArgs) Handles RadMenuItem1.Click

if (NewMDIChild Is Nothing) Then
  NewMDIChild= New InventoryForm1
  NewMDIChild.MdiParent = Me
End if

newFrm.Show()
End Sub

That way, the first time the menu item is clicked, a new instance of InventoryForm1 will be created, after that, each time the menu item is clicked the original instance will be re-opened.