But that did not work. How can i solve this?
What does "it didn't work" mean? The code in your question looks right to me.
The only reason it might not work is because the RegisterHotKey function returns an error and you are not checking for it. To make this work, you need to add the SetLastError attribute to your declaration, which is why the runtime caches the Win32 error code that it sets. Once this is done, you can check this error code (if the function returns false ) by calling the function GetLastWin32Error . I recommend using the result of this function to throw and throw a Win32Exception .
Modify the RegisterHotKey declaration as follows:
[DllImport("user32.dll", PreserveSig = false)] public static extern bool RegisterHotKey(IntPtr hWnd, int id, uint fsModifiers, Keys key);
And your function call as follows:
if (!RegisterHotKey(this.Handle, MYACTION_HOTKEY_ID, 0, Keys.F12)) { throw new Win32Exception(Marshal.GetLastWin32Error()); }
As soon as this happens, I suspect that you will see the exception received with the error message:
Hotkey already registered
Well, that makes debugging a lot easier, now no! Most likely, you need to select another hotkey, as the RegisterHotKey function documentation explicitly states that:
The F12 key is reserved for use by the debugger at any time, so it should not be registered as a hot key. Even if you do not debug the application, F12 is reserved in case the resident kernel debugging mode or the debugger is on time.
When I run the code and register F11 as a hotkey, it works fine for me.
Here I could not understand some lines, for example:
const int MYACTION_HOTKEY_ID = 1; m.Msg == 0x0312 && m.WParam.ToInt32() == MYACTION_HOTKEY_ID base.WndProc(ref m);
Can someone help me understand these lines?
Sure:
The first line declares a constant value that uniquely identifies the hotkey that you set using the RegisterHotKey function. More specifically, it corresponds to the id parameter of a function. You passed it on your first call.
The window procedure ( WndProc ) checks whether the message ( Msg ) WM_HOTKEY . The WM_HOTKEY message WM_HOTKEY automatically sent to your window when the hotkey that you registered using the RegisterHotKey function is pressed.
In fact, you should not use the magic number 0x0312 , because you are not the only one who does not know what this means. Define a constant instead and use it instead:
const int WM_HOTKEY = 0x0312; m.Msg == WM_HOTKEY
The second part of this conditional test (the part after && ) checks the wParam field of the message to see if the hotkey you registered has been pressed. Remember that MYACTION_HOTKEY_ID is the unique identifier for your hotkey. The WM_HOTKEY message WM_HOTKEY tells us that the wParam check is how we determine which hotkey was pressed.
This calls the base class window procedure. In other words, you made an overridden virtual WndProc method that allows you to add additional code (your WM_HOTKEY processing). When you are done with your additional logic, you want to continue the logic of the base class, so forward the message.