Changing ComboBox text

Reposting to a larger audience - hope someone can help!


This may seem a bit odd, but I'd like to set the text in a ComboBox control
when an item is selected from the drop down list. I want the text to be
different than the display text of the selected item.

For example, if "x" is the display text of the selected item, I want the
text in the text box to be set to "y".

I tried changing the text on SelectedIndexChanged event, but the text is set
(by the control) to the display text of the selected item *after* this
event. I've also tried TextChanged (same problem as SelectedItemChanged)
and TextUpdate (but this only fires when the user enters text directly in
the text box).

In Win32, I do this at WM_COMMAND/CBN_SELCHANGE time, which I would have
thought equates to SelectedIndexChanged in the .NET Framework.

Any ideas?

--
Michael Salamone [eMVP]
Entrek Software, Inc.
www.entrek.com

Michael
Tue Dec 20 17:59:01 CST 2005

Hey Michael,

Strange user experience, but you may use a timer to do the job, if the event
model does not help. Let's say that all of your items in the combobox have a
list value, displayed in the drop down list, and a display value that you
want to show when an item is selected.

class MyComboBoxItem {
string _listValue;
string _displayValue;

public MyComboBoxItem(string listValue, string displayValue) {
_listValue = listValue;
_displayValue = displayValue;
}

public override ToString() {
return _listValue;
}

public string DisplayValue {
get {
return _displayValue;
}
}
}


Each item added to a combobox or listbox will use the ToString() method of
the object passed to Items.Add, so you can create an object
MyComboBoxItem("x - the listed value", "y - the value to be displayed"), add
it to the combox.Item collection and the combobox will display "x - the
listed value" in it's list.

Now add a timer control to the form hosting the combobox. It will be a
performance hit, but you only need to enable it in the SelectedIndexChanged
event. In timer_tick check if (combobox.SelectedItem as
MyComboBoxItem).DisplayValue != comboBox.Text. If yes, set combobox.Text =
combobox.(SelectedItem as MyComboBoxItem).DisplayValue.

I'm not recommending this in any way, but it may do what you're looking for.

Michael



"Michael J. Salamone" <mikesa#at#entrek#dot#com> schrieb im Newsbeitrag
news:%23d7nLsVBGHA.240@TK2MSFTNGP11.phx.gbl...
> Reposting to a larger audience - hope someone can help!
>
>
> This may seem a bit odd, but I'd like to set the text in a ComboBox
> control when an item is selected from the drop down list. I want the text
> to be different than the display text of the selected item.
>
> For example, if "x" is the display text of the selected item, I want the
> text in the text box to be set to "y".
>
> I tried changing the text on SelectedIndexChanged event, but the text is
> set (by the control) to the display text of the selected item *after* this
> event. I've also tried TextChanged (same problem as SelectedItemChanged)
> and TextUpdate (but this only fires when the user enters text directly in
> the text box).
>
> In Win32, I do this at WM_COMMAND/CBN_SELCHANGE time, which I would have
> thought equates to SelectedIndexChanged in the .NET Framework.
>
> Any ideas?
>
> --
> Michael Salamone [eMVP]
> Entrek Software, Inc.
> www.entrek.com
>
>
>

Michael
Wed Dec 21 04:38:31 CST 2005

Yes, seems a strange user experience, but I think my users will actually
appreciate it. But, I can't even test it to see if I like it myself! I do
use this "technique" in some Win32 code, and the user experience is actually
pretty good. Now I've got some new UI in .net code where I want to try it.
Some things are still easier (and work!) in native!

I'll hope a better solution comes along, but I'll try the timer idea to see
how it works in this case.

Thanks.

--
Michael Salamone [eMVP]
Entrek Software, Inc.
www.entrek.com


"Michael Höhne" <michael.hoehne@nospam.nospam> wrote in message
news:%23CQAbFcBGHA.4016@TK2MSFTNGP11.phx.gbl...
> Hey Michael,
>
> Strange user experience, but you may use a timer to do the job, if the
> event model does not help. Let's say that all of your items in the
> combobox have a list value, displayed in the drop down list, and a display
> value that you want to show when an item is selected.
>
> class MyComboBoxItem {
> string _listValue;
> string _displayValue;
>
> public MyComboBoxItem(string listValue, string displayValue) {
> _listValue = listValue;
> _displayValue = displayValue;
> }
>
> public override ToString() {
> return _listValue;
> }
>
> public string DisplayValue {
> get {
> return _displayValue;
> }
> }
> }
>
>
> Each item added to a combobox or listbox will use the ToString() method of
> the object passed to Items.Add, so you can create an object
> MyComboBoxItem("x - the listed value", "y - the value to be displayed"),
> add it to the combox.Item collection and the combobox will display "x -
> the listed value" in it's list.
>
> Now add a timer control to the form hosting the combobox. It will be a
> performance hit, but you only need to enable it in the
> SelectedIndexChanged event. In timer_tick check if (combobox.SelectedItem
> as MyComboBoxItem).DisplayValue != comboBox.Text. If yes, set
> combobox.Text = combobox.(SelectedItem as MyComboBoxItem).DisplayValue.
>
> I'm not recommending this in any way, but it may do what you're looking
> for.
>
> Michael
>
>
>
> "Michael J. Salamone" <mikesa#at#entrek#dot#com> schrieb im Newsbeitrag
> news:%23d7nLsVBGHA.240@TK2MSFTNGP11.phx.gbl...
>> Reposting to a larger audience - hope someone can help!
>>
>>
>> This may seem a bit odd, but I'd like to set the text in a ComboBox
>> control when an item is selected from the drop down list. I want the
>> text to be different than the display text of the selected item.
>>
>> For example, if "x" is the display text of the selected item, I want the
>> text in the text box to be set to "y".
>>
>> I tried changing the text on SelectedIndexChanged event, but the text is
>> set (by the control) to the display text of the selected item *after*
>> this event. I've also tried TextChanged (same problem as
>> SelectedItemChanged) and TextUpdate (but this only fires when the user
>> enters text directly in the text box).
>>
>> In Win32, I do this at WM_COMMAND/CBN_SELCHANGE time, which I would have
>> thought equates to SelectedIndexChanged in the .NET Framework.
>>
>> Any ideas?
>>
>> --
>> Michael Salamone [eMVP]
>> Entrek Software, Inc.
>> www.entrek.com
>>
>>
>>
>
>

_|\|_0$P
Wed Dec 21 05:33:01 CST 2005

Hi Michael,

"Michael J. Salamone" wrote:

> Reposting to a larger audience - hope someone can help!
>
> This may seem a bit odd, but I'd like to set the text in a ComboBox control
> when an item is selected from the drop down list. I want the text to be
> different than the display text of the selected item.
>
> For example, if "x" is the display text of the selected item, I want the
> text in the text box to be set to "y".
>
> I tried changing the text on SelectedIndexChanged event, but the text is set
> (by the control) to the display text of the selected item *after* this
> event. I've also tried TextChanged (same problem as SelectedItemChanged)
> and TextUpdate (but this only fires when the user enters text directly in
> the text box).
>
> In Win32, I do this at WM_COMMAND/CBN_SELCHANGE time, which I would have
> thought equates to SelectedIndexChanged in the .NET Framework.
>
> Any ideas?
> --
> Michael Salamone [eMVP]
> Entrek Software, Inc.
> www.entrek.com

Handle the win32 events you mention from .NET code. Override the
Control.WndProc method and handle the events you mention (in that case don't
delegate to base class implementation).

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpref/html/frlrfsystemwindowsformscontrolclasswndproctopic.asp

Kind regards,
--
Tom Tempelaere.

Michael
Fri Dec 23 06:27:08 CST 2005

Very promising...

Uh, but it doesn't work :( I get the same behavior. In the WndProc, I set
the combobox Text property. But the text is then switched back. Below is
my code.

I correctly enter the block where I change the text and can view that the
text was actually changed (using the debugger). After I set the text, the
system is setting it.

[System.Security.Permissions.PermissionSet(System.Security.Permissions.SecurityAction.Demand,
Name = "FullTrust")]
protected override void WndProc(ref Message m)
{
// Listen for operating system messages.
if (m.Msg == Constants.WM_COMMAND)
{
IntPtr handle = (IntPtr) m.LParam;

if (handle == MyComboBox.Handle)
{
if (((int) m.WParam & ~0xffff) == Constants.CBN_SELCHANGE)
{
MyComboBox.Text = "Hello!";
return;
}
}
}

base.WndProc(ref m);
}


--
Michael Salamone [eMVP]
Entrek Software, Inc.
www.entrek.com


"TT (Tom Tempelaere)" <_|\|_0$P@|/\|titi____AThotmailD.Tcom|/\|@P$0_|\|_>
wrote in message news:1B61B436-C47A-425C-A2B2-4EE2969912BB@microsoft.com...
> Hi Michael,
>
> "Michael J. Salamone" wrote:
>
>> Reposting to a larger audience - hope someone can help!
>>
>> This may seem a bit odd, but I'd like to set the text in a ComboBox
>> control
>> when an item is selected from the drop down list. I want the text to be
>> different than the display text of the selected item.
>>
>> For example, if "x" is the display text of the selected item, I want the
>> text in the text box to be set to "y".
>>
>> I tried changing the text on SelectedIndexChanged event, but the text is
>> set
>> (by the control) to the display text of the selected item *after* this
>> event. I've also tried TextChanged (same problem as SelectedItemChanged)
>> and TextUpdate (but this only fires when the user enters text directly in
>> the text box).
>>
>> In Win32, I do this at WM_COMMAND/CBN_SELCHANGE time, which I would have
>> thought equates to SelectedIndexChanged in the .NET Framework.
>>
>> Any ideas?
>> --
>> Michael Salamone [eMVP]
>> Entrek Software, Inc.
>> www.entrek.com
>
> Handle the win32 events you mention from .NET code. Override the
> Control.WndProc method and handle the events you mention (in that case
> don't
> delegate to base class implementation).
>
> http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpref/html/frlrfsystemwindowsformscontrolclasswndproctopic.asp
>
> Kind regards,
> --
> Tom Tempelaere.
>