Set global hotkeys using C#

Question

I need to capture a key press when my program is not in focus. (ie. Ctrl+Alt+J) and trigger an event in my program.

Thus far i have

Answer 1

Here is a working vb.net port of original answer:

KeyboardHook.vb

Imports System.Runtime.InteropServices

Public NotInheritable Class KeyboardHook
    Implements IDisposable

    ' Registers a hot key with Windows.
     _
    Private Shared Function RegisterHotKey(hWnd As IntPtr, id As Integer, fsModifiers As UInteger, vk As UInteger) As Boolean
    End Function

    ' Unregisters the hot key with Windows.
     _
    Private Shared Function UnregisterHotKey(hWnd As IntPtr, id As Integer) As Boolean
    End Function

    ''' 

    ''' Represents the window that is used internally to get the messages.
    ''' 
    Private Class Window
        Inherits NativeWindow
        Implements IDisposable
        Private Shared WM_HOTKEY As Integer = &H312

        Public Sub New()
            ' create the handle for the window.
            Me.CreateHandle(New CreateParams())
        End Sub

        Public Event KeyPressed As EventHandler(Of KeyPressedEventArgs)

        ''' 

        ''' Overridden to get the notifications.
        ''' 
        ''' 
        Protected Overrides Sub WndProc(ByRef m As Message)
            MyBase.WndProc(m)

            ' check if we got a hot key pressed.
            If m.Msg = WM_HOTKEY Then
                ' get the keys.
                Dim key As Keys = DirectCast((CInt(m.LParam) >> 16) And &HFFFF, Keys)
                Dim modifier As ModifierKeys = DirectCast(CUInt(CInt(m.LParam) And &HFFFF), ModifierKeys)

                ' invoke the event to notify the parent.
                RaiseEvent KeyPressed(Me, New KeyPressedEventArgs(modifier, key))
            End If
        End Sub

#Region " IDisposable Members"

        Public Sub Dispose() Implements IDisposable.Dispose
            Me.DestroyHandle()
        End Sub

#End Region
    End Class

    Private _window As New Window()
    Private _currentId As Integer

    Public Sub New()
        ' register the event of the inner native window.
        AddHandler _window.KeyPressed, Sub(sender As Object, args As KeyPressedEventArgs)
                                           RaiseEvent KeyPressed(Me, args)
                                       End Sub
    End Sub

    ''' 

    ''' Registers a hot key in the system.
    ''' 
    ''' The modifiers that are associated with the hot key.
    ''' The key itself that is associated with the hot key.
    Public Sub RegisterHotKey(modifier As ModifierKeys, key As Keys)
        ' increment the counter.
        _currentId = _currentId + 1

        ' register the hot key.
        If Not RegisterHotKey(_window.Handle, _currentId, DirectCast(modifier, UInteger), CUInt(key)) Then
            'Throw New InvalidOperationException("Couldn’t register the hot key.")
            'or use MsgBox("Couldn’t register the hot key.")
        End If
    End Sub

    ''' 

    ''' A hot key has been pressed.
    ''' 
    Public Event KeyPressed As EventHandler(Of KeyPressedEventArgs)

#Region " IDisposable Members"

    Public Sub Dispose() Implements IDisposable.Dispose
        ' unregister all the registered hot keys.
        Dim i As Integer = _currentId
        While i > 0
            UnregisterHotKey(_window.Handle, i)
            System.Math.Max(System.Threading.Interlocked.Decrement(i), i + 1)
        End While

        ' dispose the inner native window.
        _window.Dispose()
    End Sub

#End Region
End Class

''' 

''' Event Args for the event that is fired after the hot key has been pressed.
''' 
Public Class KeyPressedEventArgs
    Inherits EventArgs
    Private _modifier As ModifierKeys
    Private _key As Keys

    Friend Sub New(modifier As ModifierKeys, key As Keys)
        _modifier = modifier
        _key = key
    End Sub

    Public ReadOnly Property Modifier() As ModifierKeys
        Get
            Return _modifier
        End Get
    End Property

    Public ReadOnly Property Key() As Keys
        Get
            Return _key
        End Get
    End Property
End Class

''' 

''' The enumeration of possible modifiers.
''' 
 _
Public Enum ModifierKeys As UInteger
    Alt = 1
    Control = 2
    Shift = 4
    Win = 8
End Enum

Form1.vb

Tasks:

1. Replace 2 instances of Application1 below with name of your application (it can be seen as root of tree in Visual Studio Solution Explorer window).
2. Add call to AddGlobalHotkeySupport() into initialization stage of your application.
3. Add call to RemoveGlobalHotkeySupport() into finalization stage of your application.

Code:

Public Sub AddGlobalHotkeySupport()  'TODO: call this at initialization of the application

    ' register the event that is fired after the key press.
    AddHandler hook.KeyPressed, AddressOf hook_KeyPressed

    ' register the control + alt + F12 combination as hot key.
    hook.RegisterHotKey(Application1.ModifierKeys.Control Or Application1.ModifierKeys.Alt, Keys.F12)

End Sub

Public Sub RemoveGlobalHotkeySupport()  'TODO: call this at finalization of the application
    ' unregister all registered hot keys.
    hook.Dispose()
End Sub

Private Sub hook_KeyPressed(sender As Object, e As KeyPressedEventArgs)
    ' show the keys pressed in a label.
    MsgBox(e.Modifier.ToString() + " + " + e.Key.ToString())
End Sub