Trent L. Taylor (06/07/2007)

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You can do that, but you first need to have a centralized collection that can be referenced.  You are actually better off doing this outside of the instantiaion for one primary reason...speed and maintainability...OK, that is two reasons   We created a shared class called MenuSystem which houses all of our instantiation logic.  Security, form collections, multiple-instances, and whether the form will appear in the MDI window or on its own, all within one central location.  Ours had to be a bit more specialized since it can launch VFP forms or .NET forms.  But the logic is basically the same.

You could even create a class that is passed to the MenuSystem that has all of the logic that you need that you could pass over....or just create a bunch of overloads to do this for you.  It is just up to you, but the key is creating a class that launches all of your forms according to your environment and needs.

Public Notineritable Class MenuSystem

Private Shared _MenuMdiClient As MDIClient
Private Shared _Forms As New System.Collections.Generics.List(Of SYstem.Windows.Forms.Form)

'-- Reference to the MDI client to which all client forms will be added.  Be sure to set this in your
'    New of the parent that houses the MDI client.
Public SHared Property MenuMdiClient As MDIClient
    Get
        Return _MenuMdiClient
    End Get
    Set(Byval value as MdiClient)
        _MenuMdiClient = value
    End Set
End Property

'-- This collection contains all of the forms that are loaded
Public Shared Readonly Property Forms As System.Collections.Generics.List(Of System.Windows.Forms.Form)
    Get
         Return _Forms
    End Get
End Property

'-- Central method to load all of the
Public Shared Sub LaunchForm(ByVal FormType As System.Type, Byval SecurityKey As String, Byval SingleInstance As Boolean)
    '-- Establish Locals
    Dim loForm As System.WIndows.Forms.Form

    If SecurityBasics.CurrentUser.GetPermission(SecurityKey).Action = Grant Then
       '-- Check for a single instance
       If SingleInstance AndAlso FormIsRunning(FormType) Then
            Exit Sub
       End If

       '-- Create and launch the form
        loForm = CType(Activator.CreateInstance(FormType), System.WIndows.Forms.Form)
        loForm.MdiParent = _MenuMdiClient

        '-- Create a handler so it can remove itself from the collection
        AddHandler loForm.FormClosed, Addressof HandleFormClosed

        loForm.Show()
    End If

   Private Shared Function FormIsRunning(Byval FormType As System.Type) As Boolean
     Dim llReturn As Boolean = False

      For Each loForm As Form In _Forms
         If loForm.GetType() Is FormType Then
             llReturn = True
             Exit For
         End If
      Next

      Return llReturn
    End Function

    Private Shared Sub HandleFormClosed(Byval sender as Object, Byval e as System.EventArgs)
         _Forms.Remove(CType(sender, Form))
    End Sub

End Class