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

[Dan Waters]

Good Luck Charlotte!

Lots of physical therapy ahead I'd guess - I've had good luck with that.

All the best!
Dan

-----Original Message-----
From: dba-VS [mailto:dba-vs-bounces at databaseadvisors.com] On Behalf Of
Charlotte Foust
Sent: Friday, June 05, 2015 4:53 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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