I want to create a form on a second thread that will receive messages in it's WndProc method. What is the recommended way to create an invisible form like this? Is setting "ShowInTaskbar=false" and "Visible=false" enough, or is there a "cleaner" way?
A:
As far as I know, what you're doing is against the rules (although, these things do work sometimes) ... all UI stuff is supposed to be in the main thread.
As for your question, you should be able to just set Visible to false. Setting ShowInTaskbar would only be important for the main application form, I believe, and if you did that users wouldn't have a way to get back to your app from the taskbar.
overslacked
2009-05-19 20:27:19
UI elements can be run on separate threads, as long as invoking is used to communicate between them. Ideally I would like to keep everything on 1 thread for simplicity, but in this case I have no choice.
Jon Tackabury
2009-05-20 13:41:21
+1
A:
I'm not sure what you mean by "cleaner". The standard way to create a form that is invisible to the user is to set Visible and ShowInTaskbar to false.
It's true, but I was wondering if there was a way to have a WndProc without even having the form at all. :)
Jon Tackabury
2009-05-21 18:47:52
In windows, a message loop requires a window handle. It is certainly possible to create a window handle and pass messages to it without ever actually displaying the window, but there is nothing exposed in the .NET framework to help you do that. You will have to use unmanaged APIs.
2009-05-21 20:13:48
Windows does have a message only window for that purpose, but I don't believe that is exposed in the in WinForms. See http://msdn.microsoft.com/en-us/library/ms632599%28VS.85%29.aspx#message_only
shf301
2010-02-05 02:50:25
A:
use:
Public Declare Function CreateWindowExA Lib "user32" (ByVal dwExStyle As Long, ByVal lpClassName As String, ByVal lpWindowName As String, ByVal dwStyle As Long, ByVal x As Long, ByVal y As Long, ByVal nWidth As Long, ByVal nHeight As Long, ByVal hWndParent As Long, ByVal hMenu As Long, ByVal hInstance As Long, lpParam As Any) As Long
or
Public Declare Function CreateWindowExW Lib "user32" (ByVal dwExStyle As Long, ByVal lpClassName As Long, ByVal lpWindowName As Long, ByVal dwStyle As Long, ByVal x As Long, ByVal y As Long, ByVal nWidth As Long, ByVal nHeight As Long, ByVal hWndParent As Long, ByVal hMenu As Long, ByVal hInstance As Long, lpParam As Long) As Long
note: you can change the lpClassName or lpWindowName to string or long in the declaration make sure to use "Static" as the lpClassName member - this is the invisible window style you want that is usually used for recieve wndproc windows.
the return value from this api is the hwnd(handle) that you can subclass to get the messages it will receive all standard windows messages or you can send custom messages to it, so it won't fire your code accidentally when a standard message is received.
example: hwnd_main is the hwnd of its parent window
dim hwnd_recieve as long hwnd_recieve = CreateWindowEx(num_zero, "Static", "",0,0,0,0,0, hwnd_main,0,0,0)
subclass this and have fun!
Zapf Dingbat
2010-02-05 02:11:32