Problem optaining focus when calling select in UserControl

[daniel]

Hi all,
I have a simple scenario:
I have a UserControl (control1) which hosts a TextBox. When I call
"control1.Select()", I expect to get the focus in the hosted TextBox. But it
doesn't work - the only thing I can see, is that the UserControl gets a
Enter-even.
If I host a Textbox in a Panel and then select the panel, everything works
as expected.

What do I have to do, so that my UserControl shows the correct behaviour?
Anybody has a hint?

Thanks in advance, I'm desperate :-(

Daniel

PS: I'm using .net framework 2.0, but I guess we have the same behaviour in
..net 1.1

 

[Guest]

I actually know several ways how to solve your problem, but as I was testing
it, I had the feeling this wasn't quite how it is really supposed to work...
I'm going to test a bit further. Anyway, here's already a few workarounds:

1. Calling Focus instead of Select actually selects the first child control
on the usercontrol. I saw that the UserControl captures the WM_FOCUS message
and cycles around the child controls. I am really curious what the difference
is between focusing and selecting.

2. You can override the Select method in your user control to redirect
selection to a child control using Control.Select or by using
Control.SelectNextControl.

 

[daniel]

Hi Jelle,
thanks a lot for the fast reply. Yes, the behaviour is odd and i don't know,
if I just missed something or if it's really a bug.
I know that with setting the focus with Focus() it's working. But as far as
I know you're not supposed to do that and should use Select() instead. We
had a lot of problems setting the focus manually between controls and it
ended in a "message mess".
A bug is possible. In framework 1.0 there were a lot of bugs in this area.
But I'm not sure, if I just don't know a switch and everything works fine
(like the property CanSelect or something similar). As I mentioned, Panel
works just fine. It inherits from another branch, though.
If you have the connections to find out more, I'd really appreciate it a
lot!
Anyway, thanks for your help so far.

Daniel

 

[Guest]

Hi Daniel,

I haved digged a lot deeper now and I am starting to wonder if this is not a
bug anyhow. I did not find an alternative solution than just simply
overriding the Select method and using SelectNextControl to handle the
selection yourself. I can tell you what I found out so far. I hope someone
else may shed some more light on it.

Here goes:

The difference between Focus and Select seems that Focus is a more low-level
method that directly uses Windows functions to send the WM_FOCUS message to a
control. This will not always work, for instance in the Load function, since
CanFocus will return false there. CanFocus directly checks the
IsWindowVisible and IsWindowEnabled functions, while CanSelect checks the
Control.Enabled and Control.Visible properties, which do return true in the
OnLoad method. Selecting and Focusing internally will both use the WM_FOCUS
messages. I suggest to read Jeffrey Tan's response on 'Giving a textbox the
focus', here in this newsgroup.

The Control class uses a selection scheme which tries to find the containing
control (a control that implements IContainerControl) in the parenting chain.
The ActiveControl property is set to the containercontrol.
ContainerControl.ActiveControl will eventually set the focus.

It seem that Select is a more robust mechanism, since it does not depend on
the WS_VISIBLE style that must be set on a Window. That makes me wonder why
focusing is exposed at all, but it will probably have some purpose.

The reason why I think that your specific problem might be a bug, is that I
found something odd while testing:
Upon calling Select on the usercontrol, the WM_FOCUS message is not
retrieved (I captured WM_FOCUS in the usercontrol). However, when I give
another program the focus, and switch back to my testapp, the WM_FOCUS is
suddenly send and my textbox gets the focus! I think that's fairly odd!

 

[daniel]

Hi Jelle,
thanks again! Just great, what you figured out! I myself have made a few
tests. There's a tool in codeproject which helps quite a bit and which I
often use for such puposes: ".net Control Inspector" ->
http://www.codeproject.com/csharp/controlinspector.asp

Using the tool, I made the scenario, where I called SetFocus() to my
UserControl (call it A) in the GotFocus-event of a TextBox (B).

So it looks something like that:
class Form1
{
MyUserControl ctrlA;
TextBox txtB

_txtB.GotFocus += new EventHandler(_txtB_GotFocus);

void _txtB_GotFocus(object sender, EventArgs e)
{
ctrlA.SetFocus(); //I'd like to call here ctrlA.Select()
}
}

Just for the background: I wan't to dynamically reorder the Taborder
depending on circumstances..

So what happens is quite strange: As expected the UserControl gets Enter,
then it's inner TextBox gets the Enter ...
UserControl loses Focus, the inner Textbox gets GotFocus - and also txtB
gets GotFocus!!
So at the end we see ctrlA really having the visible focus, while
technically both controls have it, because they both
got a GotFocus, while nobody in between gets a LostFocus.

I guess, it really a bug and they messed it up with the eventhandling again
:-(

Is there any other way how to find out? I think about calling in a TSC.

Have a nice evening and thanks again for your profound research on this
matter!
Daniel

 

[Guest]

Interesting, I'll have to look into this some other time. If you're confident
that this is a bug, which I'm not quite sure of, then you can file a bug
using product support:

http://lab.msdn.microsoft.com/productfeedback/

I also filed a couple of bugs there...

It seems to be the only way to get in contact with the product teams.
Unfortunately I never see Microsoft employees post in the newsgroups...

 

[daniel]

You just gave me the hint for the solution!
I went on the feedback page you mentioned and found an article:
http://lab.msdn.microsoft.com/produ...edbackid=50bca15b-ad19-435c-abe6-62ff00ec0cfc

Somebody describes a focus-bug when using Windows Classic style.
So I called "Application.EnableVisualStyles();" in my main().
This was the hint! If you use XP-style Controls, everything works as
expected
Incredible! Thanks again.
Check it out yourself, I'd like to know, if you get to the same conclusion.

 

[daniel]

Forget my last answer, I chose the wrong switch ((((! Working too long at
the same matter...
I was too euphoric ;-)