[dba-VS] Using RemoveHandler in a Combobox Base Class

[Jim Dettman]

<<I'm rusty.  I'm also having a knee replaced next week and won't be
thinking
about programming for a bit. >>

 Best wishes for a smooth process and everything goes well!

Jim.

-----Original Message-----
From: dba-VS [mailto:dba-vs-bounces at databaseadvisors.com] On Behalf Of
Charlotte Foust
Sent: Friday, June 05, 2015 05:53 PM
To: Development in Visual Studio
Subject: Re: [dba-VS] Using RemoveHandler in a Combobox Base Class

To be honest, I haven't worked seriously in VS.Net for the past 5 years, so
I'm rusty.  I'm also having a knee replaced next week and won't be thinking
about programming for a bit.  Maybe someone else will jump in and help.

Charlotte Foust
(916) 206-4336

On Fri, Jun 5, 2015 at 9:52 AM, Dan Waters <df.waters at outlook.com> wrote:

> Hi Charlotte,
>
> This is the whole story.  I have a custom control named PSICombobox which
> inherits from ComboBox.
>
> Below is shown one of the several events I've written for the PSICombobox,
> which could be used hundreds of places on many different WinForms.
>
> The issue is that when the Me.DroppedDown method is executed, the
> combobox's
> SelectedIndexChanged event on the form is automatically run, which of
> course
> can cause a problem.  I want to prevent the combobox's SelectedIndexEvent
> (on the form) from being run every time it is dropped down from the code
in
> this custom control's class.
>
> Typically I would do this in the form's code using RemoveHandler.  But
that
> requires knowing the address of the combobox, which is readily available
by
> the form's code.  But how would I get that address in the custom control's
> class code?
>
> Or, is there another way to do this without using RemoveHandler?
>
> Thanks!
> Dan
>
> '--------------------------------------------------
> Public Class PSICombobox
>
>     Inherits ComboBox
>     Protected Overrides Sub OnEnter(e As EventArgs)
>
>         If Me.Enabled = False Then Exit Sub
>
>         Me.BackColor = System.Drawing.Color.FromArgb(255, 255, 160)
> '--
> Pale Yellow
>
>         stgComboboxTextEnter = Me.Text
>
>         If Me.SelectedIndex = -1 Then
>
>             RemoveHandler Me.SelectedIndexChanged, AddressOf [WHAT GOES
> HERE?]
>
>             '-- For user convenience drop down the combobox when it gets
> the
> focus and it's empty
>             Me.DroppedDown = True
>
>             RemoveHandler Me.SelectedIndexChanged, AddressOf [WHAT GOES
> HERE?]
>
>         End If
>
>         MyBase.OnEnter(e)
>
>     End Sub
> End Class
> '--------------------------------------------------
>
> -----Original Message-----
> From: dba-VS [mailto:dba-vs-bounces at databaseadvisors.com] On Behalf Of
> Charlotte Foust
> Sent: Thursday, June 04, 2015 11:55 PM
> To: Development in Visual Studio
> Subject: Re: [dba-VS] Using RemoveHandler in a Combobox Base Class
>
> What I meant was test for a condition in that  SelectedIndexChanged event
> and then either cancel the event or handle it normally.  Is there a
> condition you could test for in that event so you would know whether to
> allow it to continue?
>
> Charlotte Foust
> (916) 206-4336
>
> On Wed, Jun 3, 2015 at 2:00 PM, Dan Waters <df.waters at outlook.com> wrote:
>
> > Hi Charlotte,
> >
> > I will add the handler back in a few lines of code down.
> >
> > What do you mean 'branching the code'?
> >
> > Dan
> >
> > -----Original Message-----
> > From: dba-VS [mailto:dba-vs-bounces at databaseadvisors.com] On Behalf Of
> > Charlotte Foust
> > Sent: Wednesday, June 03, 2015 3:40 PM
> > To: Development in Visual Studio
> > Subject: Re: [dba-VS] Using RemoveHandler in a Combobox Base Class
> >
> > Why remove the handler rather than branching the code in it?
> >
> > Charlotte Foust
> > (916) 206-4336
> >
> > On Wed, Jun 3, 2015 at 8:09 AM, Dan Waters <df.waters at outlook.com>
> wrote:
> >
> > > I have a combobox base class (a custom control) which will cause the
> > > combobox to drop down when the control is entered and the
> > > selectedindex =
> > > -1
> > > (it's empty).  This is a convenience for users.
> > >
> > >
> > >
> > > However, I recently discovered that when the combobox is dropped
> > > down, its SelectedIndexChanged event also fires, which I want to
> > > prevent. In the code behind the form, I can just use
> > >
> > >
> > >
> > > RemoveHandler cboName.SelectedIndexChanged, AddressOf
> > > cboName_SelectedIndexChanged
> > >
> > >
> > >
> > > But in the base class, I don't know how to specify what the address
> > > is for the combobox on the form.
> > >
> > >
> > >
> > > This is where I'm stuck:
> > >
> > > RemoveHandler, Me.SelectedIndexChanged, AddressOf [What is the
> > > address?]
> > >
> > >
> > >
> > > How can this be done?
> > >
> > >
> > >
> > > Thanks!
> > >
> > > Dan
> > >
> > >
> > >
> > > _______________________________________________
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> > >
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