Changing the text of a Command Button using SetWindowText

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  • Start date Start date
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support

Hi,

I am trying to change the text of a Command button using the Windows
API Function SetWindowText, which I have declared as follows:

<DllImport("User32")> _
Public Function SetWindowText(ByVal hWnd As IntPtr, ByVal
lpString As String) As Boolean
End Function

To change the text I call the function as follows in the Load event of
the form.
SetWindowText(Me.Button1.Handle.ToInt32, "TEST")
Nothing appears to happen however when I examine the Button using Spy++
it tells me the window has the text "TEST".

When I change the text of a label as follows
SetWindowText(Me.Label1.Handle.ToInt32, "TEST")
it works as expected, i.e. the change is immediately visible

I know of course that I can change the text of the button using the
syntax Button1.Text="TEST" however my objective is to use SetWindowText
as I want to change the text later in an external DLL.

It looks to me like this may be a window update issue. I have tried
invalidating the window and repainting it with no success. Can anyone
help me out on this?

Thanks in advance

Joe
 
I am trying to change the text of a Command button using the Windows
API Function SetWindowText, which I have declared as follows:

<DllImport("User32")> _
Public Function SetWindowText(ByVal hWnd As IntPtr, ByVal
lpString As String) As Boolean
End Function
Click to expand...

Specify the character set in 'DllImport' and set it to 'Auto'.
To change the text I call the function as follows in the Load event of
the form.
SetWindowText(Me.Button1.Handle.ToInt32, "TEST")
Click to expand...

Remove the '.ToInt32'.
Nothing appears to happen however when I examine the Button using Spy++
it tells me the window has the text "TEST".

When I change the text of a label as follows
SetWindowText(Me.Label1.Handle.ToInt32, "TEST")
it works as expected, i.e. the change is immediately visible
Click to expand...
It looks to me like this may be a window update issue.
Click to expand...

Maybe the reason is that .NET draws the button. You may want to test it
with native Win32 buttons and/or set the .NET button's 'FlatStyle' property
to 'System'.
 
Hi,

thanks for your help.

I tried what you suggested, it worked when I set the .NET button's
'FlatStyle' property to 'System'. It is not an option for me to
change the property however.

Can I force .NET to redraw the button using a Windows API call? I have
tried InvalidateRect and UpdateWindow without any luck.

Regards
Joe
 
Hello (e-mail address removed),

Why not simply pass the button as a parameter to your DLL ?

-Boo
 
Joe,
Is there a reason you need to use SetWindowText as opposed to simply using
Control.Text?

| Can I force .NET to redraw the button using a Windows API call? I have
| tried InvalidateRect and UpdateWindow without any luck.
I'm not certain, however I would question the need to, as Control.Text
causes the button to be redrawn...

--
Hope this helps
Jay B. Harlow [MVP - Outlook]
..NET Application Architect, Enthusiast, & Evangelist
T.S. Bradley - http://www.tsbradley.net


| Hi,
|
| thanks for your help.
|
| I tried what you suggested, it worked when I set the .NET button's
| 'FlatStyle' property to 'System'. It is not an option for me to
| change the property however.
|
| Can I force .NET to redraw the button using a Windows API call? I have
| tried InvalidateRect and UpdateWindow without any luck.
|
| Regards
| Joe
|
| Herfried K. Wagner [MVP] schrieb:
|
| > > I am trying to change the text of a Command button using the Windows
| > > API Function SetWindowText, which I have declared as follows:
| > >
| > > <DllImport("User32")> _
| > > Public Function SetWindowText(ByVal hWnd As IntPtr, ByVal
| > > lpString As String) As Boolean
| > > End Function
| >
| > Specify the character set in 'DllImport' and set it to 'Auto'.
| >
| > > To change the text I call the function as follows in the Load event of
| > > the form.
| > > SetWindowText(Me.Button1.Handle.ToInt32, "TEST")
| >
| > Remove the '.ToInt32'.
| >
| > > Nothing appears to happen however when I examine the Button using
Spy++
| > > it tells me the window has the text "TEST".
| > >
| > > When I change the text of a label as follows
| > > SetWindowText(Me.Label1.Handle.ToInt32, "TEST")
| > > it works as expected, i.e. the change is immediately visible
| >
| > > It looks to me like this may be a window update issue.
| >
| > Maybe the reason is that .NET draws the button. You may want to test it
| > with native Win32 buttons and/or set the .NET button's 'FlatStyle'
property
| > to 'System'.
| >
| > --
| > M S Herfried K. Wagner
| > M V P <URL:http://dotnet.mvps.org/>
| > V B <URL:http://classicvb.org/petition/>
|
 
Doh! missed the lower half of the question here.


| I know of course that I can change the text of the button using the
| syntax Button1.Text="TEST" however my objective is to use SetWindowText
| as I want to change the text later in an external DLL.
I missed the part of the external DLL.

Is the external DLL written in unmanaged C/C++ or is it a managed (VB, C#)
dll?

If its a managed Dll; Why not simply pass Button or Control to the external
DLL allowing it to use Control.Text?

--
Hope this helps
Jay B. Harlow [MVP - Outlook]
..NET Application Architect, Enthusiast, & Evangelist
T.S. Bradley - http://www.tsbradley.net


|
| Hi,
|
| I am trying to change the text of a Command button using the Windows
| API Function SetWindowText, which I have declared as follows:
|
| <DllImport("User32")> _
| Public Function SetWindowText(ByVal hWnd As IntPtr, ByVal
| lpString As String) As Boolean
| End Function
|
| To change the text I call the function as follows in the Load event of
| the form.
| SetWindowText(Me.Button1.Handle.ToInt32, "TEST")
| Nothing appears to happen however when I examine the Button using Spy++
| it tells me the window has the text "TEST".
|
| When I change the text of a label as follows
| SetWindowText(Me.Label1.Handle.ToInt32, "TEST")
| it works as expected, i.e. the change is immediately visible
|
| I know of course that I can change the text of the button using the
| syntax Button1.Text="TEST" however my objective is to use SetWindowText
| as I want to change the text later in an external DLL.
|
| It looks to me like this may be a window update issue. I have tried
| invalidating the window and repainting it with no success. Can anyone
| help me out on this?
|
| Thanks in advance
|
| Joe
|
 
Hi,

that is how my DLL is supposed to work. It takes the window handle as a
parameter and changes the text using the Windows API call
SetWindowText.

That doesn't work either though, so to localise the problem I
simplified it to a direct call to SetWindowText in vb.net.

Joe
 
Hi Jay,

its an unmanaged C++ DLL.

The curious thing is if I set the text of the button using
SetWindowText to say "XYZ" and then read it back using GetWindowText I
get "XYZ" as a result.

It just doesn't display the text I set even if I repaint the screen. If
however I change the flatstyle of the button to system, then it works.
Problem is that is not an option.


Regards
Joe
 
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