Is this normal

  • Thread starter Thread starter Robert Brown
  • Start date Start date
R

Robert Brown

Hi there,

Is it normal for form-based events to fire in "InitializeComponent()". I've
got a "DataGridView" on a form and I set its "CellValueChanged" event using
the forms designer. Ok, VS initializes my event in "InitializeComponent()".
However, "InitializeComponent()" later calls
"ComponentResourceManager.ApplyResources()" which (to my great surprise)
fires my event (which my handler then chokes on since it thinks the window
is already running). Looking at the call stack, the event was fired while
initializing the header text on one of my "DataGridView" columns (from the
resource file). I'm not sure if this particular event should even apply in
this situation but in any case, the form hasn't even been created yet. Is it
therefore normal for some form-based events to be fired while the
constructor is still running. If so then it's potentially dangerous to
define events using the forms designer so we should presumably add them
ourselves in "OnLoad()" typically (or otherwise design all handlers to check
that the window has actually been created which is ugly IMO). Can anyone
elaborate on this situation. Thanks.
 
Robert Brown said:
Hi there,

Is it normal for form-based events to fire in "InitializeComponent()".
I've got a "DataGridView" on a form and I set its "CellValueChanged" event
using the forms designer. Ok, VS initializes my event in
"InitializeComponent()". However, "InitializeComponent()" later calls
"ComponentResourceManager.ApplyResources()" which (to my great surprise)
fires my event (which my handler then chokes on since it thinks the window
is already running). Looking at the call stack, the event was fired while
initializing the header text on one of my "DataGridView" columns (from the
resource file). I'm not sure if this particular event should even apply in
this situation but in any case, the form hasn't even been created yet. Is
it therefore normal for some form-based events to be fired while the
Click to expand...
Yes, that happens.
constructor is still running. If so then it's potentially dangerous to
define events using the forms designer so we should presumably add them
ourselves in "OnLoad()" typically (or otherwise design all handlers to
check that the window has actually been created which is ugly IMO). Can
anyone elaborate on this situation. Thanks.
Click to expand...

The designer registers events as the last thing it does for any control.
Usually that's good enough. In a couple cases you have to register the
handler later yourself, I've seen that too.
 
Is it normal for form-based events to fire in "InitializeComponent()".
Yes, that happens.
Click to expand...

Ok, thanks for the confirmation. It's arguably a questionable design however
since these events really seem to be intended for the post-window (creation)
environment. It's even possible for this problem not to surface until your
program has been released (though in practice it's likely to be caught long
before that).
The designer registers events as the last thing it does for any control.
Usually that's good enough. In a couple cases you have to register the
handler later yourself, I've seen that too.
Click to expand...

Ok, I'll exercise caution from now on. Thanks again.
 
Don't set the event in design mode. Do it in your Form_Load routine.
That will take care of your problem.

Robin S.
-------------------------
 
Back
Top