Develop Reference

Control taskbar blinking event of an other application

I want to build a c# desktop application which checks the taskbar blinking event of a specific program. When ever the programs taskbar blinking event occurs my application will play an alarm sound. Is it possible and where to start please ?

One way would be to use something like EasyHook and basically replace the processes call to FlashWindowEx function.
However because you don't directly control this application it is likely to be error prone.

C# - Transparent Window to defeat Keyloggers

How can I create a window which is fully apparent to the user but is not visible in screenshots. I know that this is possible since Neo SafeKeys (an onscreen keyboard to defeat keyloggers) does not appear in the screenshots taken by keylogging software I installed.
To give you an idea, the window is fully visible to the user, however when a screenshot is taken, the Neo SafeKeys window does not appear at all (as if it does not even exist).
Neo SafeKeys states that it uses an invisible protection layer above the window to protect against screenshots. I have searched all over the internet to see how can I reproduce this, to no avail. Does anybody know how this can be performed (windows which is visible to user but invisible in screenshots)?

What you can do is you can prevent the PrtScn key from doing anything when pressed. Take a look at this article while shows you how to do this.
What this article is doing is clearing out the clipboard. What you can do instead is capture the screen image and digitally remove your application, then put the revised image on the clipboard, thus giving the "Effect" of making your window transparent.
Also, you might want to look at this SO question which gives an alternative way to make your window just appear "blue", though its not easy to do.

Does anybody know how this can be performed (windows which is visible to user but invisible in screenshots)?
Use DirectX to render directly to the device.

In your C# application you can set up a global hook to monitor keyboard events. Then your application becomes the global handler for print screens. Now if another application managed screen prints natively, can't stop that, but anything running through windows, you can get at.
The WM_KEYBOARD_LL hook is one of the few global hooks that can be used in managed code because it doesn't require a DLL to be injected into every target.
For some code you can visit here:
Adam's Blog
Keep in mind that these are global hooks so you want to make sure nothing else (other applications) are effected. I've used these in the past as we hosted showing a power point in an application we worked on. Basically we didn't want the user to invoke any powerpoint menus or keyboard short cuts so we used a global hook. We always checked to see whether the users was in a certain area (screen) and in our application, otherwise we would effect other applications functionality (including our own!)
Microsoft Information:
Hooks Overview

There's this.....
visual cryptography
live example here
But this could be easily coded against by taking multiple screenshots and laying them overeachother and such...

If you are using Windows, and you can avoid that screenlogging happens, you can implement a nice solution like a virtual desktop to embed your process into it. When a process is running inside a virtual desktop it is possible to bypass an screenlogger tool that runs over win32 Api.
Check out this article so you can sneak a peek how to implement a nice solution to scape from screen and keyboard monitoring.
http://www.codeproject.com/Articles/7392/Lock-Windows-Desktop?fid=62485&select=3139662&fr=101#xx0xx

Intercepting and hiding a window before it appears

I am developing a (in-process) plug-in to application and as part of my plug-in I want to replace the application's tool-tips with my own. However, there is no API available for me to do so, so I've decided to go low-level.
I know the window class of the tool tip, but the question is, how do I detect it being created and how do I close it afterward?
Here's what I thought to do so far:
Create a system-wide hook on WM_CREATE
When caught, check the class and the process of the WM_CREATE target
Verify it is indeed the window I care about:
If the process is the one my plug-in is sitting in
And if the class is of the correct type
And if the correct application is in focus (in case of multiple applications)
Send a WM_DESTROY to the created window and create my own window at its position instead
How does it sound? Assuming there is indeed no API to handle the tooltips, is there a simpler way for what I need?
Thanks!
P.S Tagged as C++/C# as I intend to write it in these 2 languages (C++ for system-wide hook, C# for everything else)

If you know the type of the window you want to block, you can simply subclass it and handle the destruction in your own WndProc. Use GetClassLongPtr() with GCL_WNDPROC on the tooltip class, use SetClassLongPtr() with GCL_WNDPROC to set your own WndProc and have it call DestroyWindow() on WM_CREATE and call the old WndProc for the rest..

This won't work. Consider the view of the application that you're replacing the tooltips of and assuming that you could tell it to destroy windows. What will happen when the app decides that it needs to close the tooltip? It doesn't have the handle of your new window, it has the handle of the old window, which you've destroyed. Time for things to go wrong.
Your plugin system needs to explicitly support replacing the tooltips if you want this to work smoothly. Perhaps an optional part of the plugin framework could be a RequestTooltip function. If it doesn't exist, or returns null, or whatever then the default tooltips are used, otherwise your plugin provided ones are used.

Prevent Process 'A' from spawning Process 'B' which then shows up on top of what should be the "TopMost" Process 'C'

I have a windows form application which needs to be the TopMost. I've set my form to be the TopMost and my application works as I'd like it to except for in one case.
There is a 3rd party application (referred to as player.exe) that displays SWF movie files on a portion of the screen that popup on top of my application.
Using Process Monitor I determined that player.exe application calls
flash.exe <PositionX> <PositionY> <Width> <Height> <MovieFile>
in my case:
flash.exe 901 96 379 261 somemovie.swf
Since flash.exe is being spawned in a new process after my form has been set to the TopMost it is appearing on top of my application.
First thing I did was make my application minimize the player.exe main application window hoping that this would prevent the Flash from appearing also. But, unfortunately it doesn't... even with the window minimized whenever the flash movie starts it shows up at the pixel location (901,96). I then tried creating a timer to keep setting the form.TopMost property to true every 10ms. This sort of works but you still see a very quick blip of the swf file.
Is there some type of Windows API call which can be used to temporarily prevent player.exe from spawning child processes which are visible? I admit it sounds a little far fetched. But, curious if anyone else has had a similar problem.
Addendum:
This addendum is to provide a reply to some of the suggestions layed out in Mathew's post below.
For the emergency situation described in the comments, I would look at possible solutions along these lines:
1) How does the third party application normally get started and
stopped? Am I permitted to close it
the same way? If it is a service, the
Service Control Manager can stop it.
If it is a regular application,
sending an escape keystroke (with
SendInput() perhaps) or WM_CLOSE
message to its main window may work.
Easiest way to close the app is to CTRL-ALT-DEL, then kill process. -OR-
The proper way is to Hold ESC while clicking the left mouse button... then input your username and password, navigate some menu's to stop the player.
There is no PAUSE command... believe it or not.
I don't think using WM_CLOSE will help since minimizing the application doesn't. Would that kill the process also? If not, how do you reopen it.
2) If I can't close it nicely, am I permitted to kill it? If so,
TerminateProcess() should work.
I can't kill the process for two reasons. 1) Upon relaunch you need to supply username/password credentials... There may be a way to get around this since it doesn't prompt when the machine is rebooted but... 2) Whenever I kill the process in task manager it doesn't die gracefully and asks if you want to send an error report.
3) If I absolutely have to leave the other process running, I would try
to see if I can programmatically
invoke fast user switching to take me
to a different session (in which there
will be no competing topmost windows).
I don't know where in the API to start
with this one. (Peter Ruderman
suggests SwitchDesktop() for this
purpose in his answer.)
I got really excited by this idea... I found this article on CodeProject which provides a lot of the API Wrapper methods. I stopped implementing it because I think that in order for desktop's to work you must have explorer.exe running (which I do not).
EDIT2: On second thought... maybe explorer.exe isn't needed. I'll give it a try and report back.
Edit3: Was unable to get the code in that article working. Will have to put this on hold for a moment.
Answer Summary
As one might have expected, there is no simple answer to this problem. The best solution would be to problematically switch to a different desktop when you need to guarantee nothing will appear over it. I was unable to find a simple C# implementation of desktop switching that worked and I had a looming doubt that I would just be opening a whole new set of worms once it was implemented. Therefore, I decided not to implement the desktop switching. I did find a C++ Implementation that works well. Please post working C# virtual desktop implementations for others.

Setting the TopMost property (or adding the WS_EX_TOPMOST style to a window) does not make it unique in the system. Any number of topmost windows may be created by any number of applications; the only guarantee is that all topmost windows will be drawn 'above' all non-topmost windows. If there are two or more topmost windows, the Z-order still applies. From your description, I suspect that flash.exe is also creating a topmost window.
Aside from periodically forcing your window to the top of the Z-order, I think there is little you can do. Be warned, however, that this approach is dangerous: if two or more windows are simultaneously trying to force themselves to the top of the Z-order, the result will be a flickering mess that the user will likely have to use the task manager to escape.
I recommend that your program not attempt to meddle with other processes on the computer (unless that is its explicit purpose, e.g. a task manager clone). The computer belongs to the user, and he may not value your program more highly than all others.
Addendum:
For the emergency situation described in the comments, I would look at possible solutions along these lines:
How does the third party application normally get started and stopped? Am I permitted to close it the same way? If it is a service, the Service Control Manager can stop it. If it is a regular application, sending an escape keystroke (with SendInput() perhaps) or WM_CLOSE message to its main window may work.
If I can't close it nicely, am I permitted to kill it? If so, TerminateProcess() should work.
If I absolutely have to leave the other process running, I would try to see if I can programmatically invoke fast user switching to take me to a different session (in which there will be no competing topmost windows). I don't know where in the API to start with this one. (Peter Ruderman suggests SwitchDesktop() for this purpose in his answer.)

You can use the Process class to start flash.exe directly - and use an appropriate ProcessStartInfo settings to show the window in a hidden state - or with a WindowStyle of hidden or minimized.
You could also consider using the SetWindowsHookEx API to intercept the process start API calls, and when the process is flash.exe run some code to restore you window to top-most status.

Matthew's answer is excellent, but I suspect you may be asking the wrong question. Why does your application need to be topmost? If you're trying to create a kiosk or some such, then topmost is not the way to go.
Edit: After reading your response to Matthew's comment, I'd suggest creating a new desktop and switching to it before displaying your alert. (See CreateDesktop and SwitchDesktop in MSDN.)

Sending a mouse click to a button in the taskbar using C#

In an application that I am currently working on, a requirement is to bring a window of an external application to the foreground. Making Win32 API calls such as BringWindowToTop and SetForeground window do not work all the time. This is due to some restrictions within Windows XP. What I would like to do instead is send simulate a mouse click the window's button on the taskbar which I am hoping will bring the window to the front. Does anyone know how this is possible?

Check out the section "How to steal focus on 2K/XP" at http://www.codeproject.com/KB/dialog/dlgboxtricks.aspx, as this is exactly what you need. I wouldn't go the taskbar route as the taskbar could be hidden or simply not there.

It's possible. But it's extremely sketchy. Your application may also break with the next version of Windows, since it's undocumented. What you need to do is find the window handle of the taskbar, then find the window handle of the child window representing the button, then send it a WM_MOUSEDOWN (I think) message.
Here's a bit on finding the window handle of the taskbar:
http://www.codeproject.com/
FWIW, the restrictions on BringWindowToTop/SetForeground are there because it's irritating when a window steals focus. That may not matter if you're working on a corporate environment. Just keep it in mind. :)

I used this in a program where I needed to simulate clicks and mouse movements;
Global Mouse and Keyboard Library

To be honest I've never had an issue bringing a window to the foreground on XP/Vista/2003/2000.
You need to make sure you do the following:
Check if IsIconic (minimized)
If #1 results in true then call
ShowWindow passing SW_RESTORE
Then call SetForegroundWindow
I've never had problems that I can think of doing it with those steps.