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Posted on 2006-06-07
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Last Modified: 2011-09-20
How can I create window with valid handle without showing it?
My problem is that I have form with some object in it, which should be initialized with form handle. When form is just created, in constructor, handle is invalid. Handle is created only when form is shown first time. Form.CreateHandle Method shows the form, so I cannot use it.
Currently I make initialization when form is shown first time, and this is not nice. I need a way to create invisible form with valid window handle.

Environment: C# 2005, Windows Forms.
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Question by:AlexFM
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Assisted Solution

by:God_Ares
God_Ares earned 1000 total points
ID: 16851076
What kind of component?

Will the object accept a intptr.null (well you understand what I'm aiming at)...

On the other hand you have to ask yourself Why does it need a handle,..? Maybe it needs to read Windows Messages for some reason.. I'm sure it woudn't be there if it wasn't nessesary.

Creating a window on the fly is possible (consider making it a borderless window with size 1,1 and location 0,0). You can even do this with a new form..

But I think your current solutuin (creating it on form_load right?) is a good one, with the infromation you gave to us.

regards

Floris

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by:AlexFM
ID: 16851233
This is my own class written in C++, it requires window handle for initialization. And this is really necessary :)
My current solution is working, but I don't like it. For example, initialization can fail, and I hide this window immediately. In this case window is shown for a short time and disappears.
There should be way to do this. In Win32 programming this is very simple - just create window without WS_VISIBLE style.
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Accepted Solution

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Bob Learned earned 1000 total points
ID: 16851356
Alex,

I override the CreateParams to set window styles for controls.  Here is an example for a form:

Creating Mirrored Windows Forms and Controls
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vbcon/html/vbtskCreatingMirroredWindowsFormsControls.asp

protected override CreateParams CreateParams
{
    get
    {
        CreateParams CP = base.CreateParams;
        if (! base.DesignMode)
            CP.ExStyle = CP.ExStyle | WS_EX_LAYOUTRTL | WS_EX_NOINHERITLAYOUT;
        return CP;
    }
}

Bob
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LVL 48

Author Comment

by:AlexFM
ID: 16851632
Sorry, TheLearnedOne, I don't see how this helps. Maybe you posted in wrong question by mistake?  :-)
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Expert Comment

by:Bob Learned
ID: 16851739
Alex,

You said, "just create window without WS_VISIBLE style."

And I showed a way of getting at the window parameters to remove the WS_VISIBLE style property.

Bob
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LVL 48

Author Comment

by:AlexFM
ID: 16851867
OK, now I see, thank you.
I have a lot of other problems using .NET window handle in C++ code, because .NET can change window handle on the fly when window is hidden and shown again. I need to change algorithm completely, keep form reference and extract handle dynamically when necessary - a lot of changes, but at least I learned something.
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