Access MDI child properties generically

14 May 2006 1:55 AM

Mark Hoffy

Hello,

I have an MDI app. There are many child forms and they all have several
things in common. They all have a Save button, a public variable
boolNavigate, and they all have a TreeView called treeBrowse.

I have a generic routine to create the TreeView and add it to a form since I
do this on a dozen or so forms. I also would like to add event handlers in
this generic routine. The handler routines perform the same function on
every form, but they need to reference the boolNavigate variable of the
particular calling form. How can I do this without typing the form in a
case with every possible child form?

Here is my code from a librabry module...

   Public Sub CreateBrowserTree(ByVal frmParent As Form, ByVal treeIn As
TreeView)
        'sets up a generic browser tree view attached to the passed in
parent control
        Dim splitBrowse As Splitter

        'create a splitter
        splitBrowse = New Splitter
        With splitBrowse
            '...set properties
        End With
        frmParent.Controls.Add(splitBrowse)

        'create a tree
        treeIn = New TreeView
        With treeIn
                   '...set properties
        End With
        frmParent.Controls.Add(treeIn)

        'attach event handlers
        AddHandler treeIn.BeforeSelect, AddressOf TreeBrowse_BeforeSelect
        '.... more of same type handlers
    End Sub

    Private Sub TreeBrowse_BeforeSelect(ByVal sender As Object, ByVal e As
System.Windows.Forms.TreeViewCancelEventArgs)
        'dont allow user to leave this node if bollNavigate is false
        If (not sender.boolNavigate) Then
            Beep()
            e.Cancel = True
        End If
    End Sub

The part about 'sender.boolNavigate' does not work. How can I access this
property that I know exists for every given form?

Also, I the code for each form's 'Save' button is the same. Is there a way
I can make a generic handler for that and have it apply to all the forms so
I can maintain 1 routine? Currently every form's save routine looks about
like this...

   Private Sub cmdSave_Click(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles cmdSave.Click
        If (SaveFormData(boolAddingNew, me) Then    'SaveFormData is a
generic data saving routine, pass a flag for new and the parent control
(form)
                'reload the data
                LoadFormData()           'this routine is different on each
form, but the Save handler would call each form's version
                FirstNode(treeBrowse)
                cmdNew.Enabled = True     'again, each form has a cmdNew
        End If
    End Sub

Thanks in advance.

16 May 2006 2:21 PM

CMM

I'm not really sure if I completely understand the problem... but from what
I could surmise, wouldn't having your child forms implement an Interface
solve your problems?

First off, for the love of god, wrap the boolNavigate var into a Property
called "AllowNavigate" or something. Add a new Interface file:

Interface IMyChildForm
    Property AllowNavigate As Boolean
End Interface

Then add "Implements IMyChildForm" to all your forms.

Then you use as so:

If Not DirectCast(Sender, IMyChildForm).AllowNavigate Then
    Beep()
    e.Cancel = True
End If

--
-C. Moya
www.cmoya.com

Show quoteHide quote

"Mark Hoffy" <m***@here.com> wrote in message
news:81w9g.1889$Jn3.412@fe04.lga...
> Hello,
>
> I have an MDI app. There are many child forms and they all have several
> things in common. They all have a Save button, a public variable
> boolNavigate, and they all have a TreeView called treeBrowse.
>
> I have a generic routine to create the TreeView and add it to a form since
> I
> do this on a dozen or so forms. I also would like to add event handlers
> in
> this generic routine. The handler routines perform the same function on
> every form, but they need to reference the boolNavigate variable of the
> particular calling form. How can I do this without typing the form in a
> case with every possible child form?
>
> Here is my code from a librabry module...
>
>   Public Sub CreateBrowserTree(ByVal frmParent As Form, ByVal treeIn As
> TreeView)
>        'sets up a generic browser tree view attached to the passed in
> parent control
>        Dim splitBrowse As Splitter
>
>        'create a splitter
>        splitBrowse = New Splitter
>        With splitBrowse
>            '...set properties
>        End With
>        frmParent.Controls.Add(splitBrowse)
>
>        'create a tree
>        treeIn = New TreeView
>        With treeIn
>                   '...set properties
>        End With
>        frmParent.Controls.Add(treeIn)
>
>        'attach event handlers
>        AddHandler treeIn.BeforeSelect, AddressOf TreeBrowse_BeforeSelect
>        '.... more of same type handlers
>    End Sub
>
>    Private Sub TreeBrowse_BeforeSelect(ByVal sender As Object, ByVal e As
> System.Windows.Forms.TreeViewCancelEventArgs)
>        'dont allow user to leave this node if bollNavigate is false
>        If (not sender.boolNavigate) Then
>            Beep()
>            e.Cancel = True
>        End If
>    End Sub
>
> The part about 'sender.boolNavigate' does not work. How can I access this
> property that I know exists for every given form?
>
> Also, I the code for each form's 'Save' button is the same. Is there a
> way
> I can make a generic handler for that and have it apply to all the forms
> so
> I can maintain 1 routine? Currently every form's save routine looks about
> like this...
>
>   Private Sub cmdSave_Click(ByVal sender As System.Object, ByVal e As
> System.EventArgs) Handles cmdSave.Click
>        If (SaveFormData(boolAddingNew, me) Then    'SaveFormData is a
> generic data saving routine, pass a flag for new and the parent control
> (form)
>                'reload the data
>                LoadFormData()           'this routine is different on each
> form, but the Save handler would call each form's version
>                FirstNode(treeBrowse)
>                cmdNew.Enabled = True     'again, each form has a cmdNew
>        End If
>    End Sub
>
> Thanks in advance.
>
>