IntPtr hWnd = WindowFromPoint(pt);

GetWindowThreadProcessId(hWnd, out pid);

public delegate int BrowseCallbackProc(IntPtr hwnd, int uMsg, IntPtr lParam, IntPtr lpData);

Public Delegate Function BrowseCallbackProc(hwnd As IntPtr, uMsg As Integer, lParam As IntPtr, lpData As IntPtr) As Integer

private delegate bool EnumWindowsProc(IntPtr hWnd, IntPtr lParam);

Private Delegate Function EnumWindowsProc(ByVal hWnd As IntPtr, ByVal lParam As IntPtr) As Boolean

If you’re going to use the lParam to return a by-value result (such as the hwnd of a window you are looking for), you’ll want to send lParam by reference:

private delegate bool EnumWindowsProc(IntPtr hWnd, ref IntPtr lParam);

Private Delegate Function EnumWindowsProc(ByVal hWnd As IntPtr, ByRef lParam As IntPtr) As Boolean

hwnd in Type: HWND A handle to the window associated with the timer.

delegate IntPtr WndProc (IntPtr hWnd, uint msg, IntPtr wParam, IntPtr lParam);

Delegate Function WndProc (ByVal hWnd As IntPtr, ByVal msg As Integer, _

private delegate IntPtr WndProc(IntPtr hWnd, uint msg, IntPtr wParam, IntPtr lParam);

Private Delegate Function WndProc(ByVal hWnd As IntPtr, ByVal msg As UInteger, ByVal wParam As IntPtr, ByVal lParam As IntPtr) As IntPtr

LRESULT APIENTRY buttonPlsVisibleProc(HWND hWnd, UINT Msg, WPARAM wParam, LPARAM lParam)

            MessageBox(hWnd, L"Hello bn", NULL, MB_OK);

        //MoveWindow(hWnd, r.right - 28, 6, 24, 24, TRUE);

        //SetBitmap(hWnd, (isPlaylistVisible ? IDB_RESTORE_PRESSED : IDB_CLOSE_PRESSED));

        //MoveWindow(hWnd, r.right - 29, 5, 24, 24, TRUE);

        //SetBitmap(hWnd, (isPlaylistVisible ? IDB_RESTORE_NORMAL : IDB_CLODE_NORMAL));

    return CallWindowProc(buttonPlsVisible_proc, hWnd, Msg, wParam, lParam);

            public const uint GW_HWNDFIRST = 0;

            public const uint GW_HWNDLAST = 1;

            public const uint GW_HWNDNEXT = 2;

            public const uint GW_HWNDPREV = 3;

            public const uint GW_HWNDFIRST = 0;

            public const uint GW_HWNDLAST = 1;

            public const uint GW_HWNDNEXT = 2;

            public const uint GW_HWNDPREV = 3;

    GW_HWNDFIRST = 0

    GW_HWNDLAST = 1

    GW_HWNDNEXT = 2

    GW_HWNDPREV = 3

static readonly int GWL_HWNDPARENT = -8;

Public Const GWL_HWNDPARENT = -8

     GWLP_HWNDPARENT = -8,

public const IntPtr HWND_BROADCAST = new IntPtr(0xffff);

public const IntPtr HWND_TOP       = new IntPtr(0);

public const IntPtr HWND_BOTTOM    = new IntPtr(1);

public const IntPtr HWND_TOPMOST   = new IntPtr(-1);

public const IntPtr HWND_NOTOPMOST = new IntPtr(-2);

public const IntPtr HWND_MESSAGE   = new IntPtr(-3);

Public Const HWND_BROADCAST As Int32 = &HFFFF

Public Const HWND_TOP As Int32       = &H0

Public Const HWND_BOTTOM As Int32    = &H1

Public Const HWND_TOPMOST As Int32   = -&H1

Public Const HWND_NOTOPMOST As Int32 = -&H2

Public Const HWND_MESSAGE As Int32   = -&H3

public static IntPtr HWND_MESSAGE = new IntPtr(-3);

    // (HIMAGELIST)SNDMSG((hwnd), TCM_GETIMAGELIST, 0, 0L)

    // (HIMAGELIST)SNDMSG((hwnd), TCM_SETIMAGELIST, 0, (LPARAM)(UINT)(HIMAGELIST)(himl))

    // (int)SNDMSG((hwnd), TCM_GETITEMCOUNT, 0, 0L)

    // (BOOL)SNDMSG((hwnd), TCM_GETITEM, (WPARAM)(int)iItem, (LPARAM)(TC_ITEM FAR*)(pitem))

    // (BOOL)SNDMSG((hwnd), TCM_SETITEM, (WPARAM)(int)iItem, (LPARAM)(TC_ITEM FAR*)(pitem))

    // (int)SNDMSG((hwnd), TCM_INSERTITEM, (WPARAM)(int)iItem, (LPARAM)(const TC_ITEM FAR*)(pitem))

    // (BOOL)SNDMSG((hwnd), TCM_DELETEITEM, (WPARAM)(int)(i), 0L)

    // (BOOL)SNDMSG((hwnd), TCM_DELETEALLITEMS, 0, 0L)

    // (BOOL)SNDMSG((hwnd), TCM_GETITEMRECT, (WPARAM)(int)(i), (LPARAM)(RECT FAR*)(prc))

    // (int)SNDMSG((hwnd), TCM_GETCURSEL, 0, 0)

    // (int)SNDMSG((hwnd), TCM_SETCURSEL, (WPARAM)i, 0)

    // (int)SNDMSG((hwndTC), TCM_HITTEST, 0, (LPARAM)(TC_HITTESTINFO FAR*)(pinfo))

    // (BOOL)SNDMSG((hwndTC), TCM_SETITEMEXTRA, (WPARAM)(cb), 0L)

    // (int)SNDMSG(hwnd, TCM_ADJUSTRECT, (WPARAM)(BOOL)bLarger, (LPARAM)(RECT FAR *)prc)

    // (DWORD)SNDMSG((hwnd), TCM_SETITEMSIZE, 0, MAKELPARAM(x,y))

    //     (void)SNDMSG((hwnd), TCM_REMOVEIMAGE, i, 0L)

    //     (void)SNDMSG((hwnd), TCM_SETPADDING, 0, MAKELPARAM(cx, cy))

    //     (int)SNDMSG((hwnd), TCM_GETROWCOUNT, 0, 0L)

    // (int)SNDMSG((hwnd), TCM_GETCURFOCUS, 0, 0)

    // SNDMSG((hwnd),TCM_SETCURFOCUS, i, 0)

    //     (int)SNDMSG((hwnd), TCM_SETMINTABWIDTH, 0, x)

    //     (void)SNDMSG((hwnd), TCM_DESELECTALL, fExcludeFocus, 0)

    // (BOOL)SNDMSG((hwnd), TCM_HIGHLIGHTITEM, (WPARAM)i, (LPARAM)MAKELONG (fHighlight, 0))

    //     (DWORD)SNDMSG((hwnd), TCM_SETEXTENDEDSTYLE, 0, dw)

    //     (DWORD)SNDMSG((hwnd), TCM_GETEXTENDEDSTYLE, 0, 0)

    '     (HIMAGELIST)SNDMSG((hwnd), TCM_GETIMAGELIST, 0, 0L)

    '     (HIMAGELIST)SNDMSG((hwnd), TCM_SETIMAGELIST, 0, (LPARAM)(UINT)(HIMAGELIST)(himl))

    '     (int)SNDMSG((hwnd), TCM_GETITEMCOUNT, 0, 0L)

    '     (BOOL)SNDMSG((hwnd), TCM_GETITEM, (WPARAM)(int)iItem, (LPARAM)(TC_ITEM FAR*)(pitem))

    '     (BOOL)SNDMSG((hwnd), TCM_SETITEM, (WPARAM)(int)iItem, (LPARAM)(TC_ITEM FAR*)(pitem))

    '     (int)SNDMSG((hwnd), TCM_INSERTITEM, (WPARAM)(int)iItem, (LPARAM)(const TC_ITEM FAR*)(pitem))

    '     (BOOL)SNDMSG((hwnd), TCM_DELETEITEM, (WPARAM)(int)(i), 0L)

    '     (BOOL)SNDMSG((hwnd), TCM_DELETEALLITEMS, 0, 0L)

    '     (BOOL)SNDMSG((hwnd), TCM_GETITEMRECT, (WPARAM)(int)(i), (LPARAM)(RECT FAR*)(prc))

    '     (int)SNDMSG((hwnd), TCM_GETCURSEL, 0, 0)

    '     (int)SNDMSG((hwnd), TCM_SETCURSEL, (WPARAM)i, 0)

    '     (int)SNDMSG((hwndTC), TCM_HITTEST, 0, (LPARAM)(TC_HITTESTINFO FAR*)(pinfo))

    '     (BOOL)SNDMSG((hwndTC), TCM_SETITEMEXTRA, (WPARAM)(cb), 0L)

    '     (int)SNDMSG(hwnd, TCM_ADJUSTRECT, (WPARAM)(BOOL)bLarger, (LPARAM)(RECT FAR *)prc)

    '     (DWORD)SNDMSG((hwnd), TCM_SETITEMSIZE, 0, MAKELPARAM(x,y))

    '     (void)SNDMSG((hwnd), TCM_REMOVEIMAGE, i, 0L)

    '     (void)SNDMSG((hwnd), TCM_SETPADDING, 0, MAKELPARAM(cx, cy))

    '     (int)SNDMSG((hwnd), TCM_GETROWCOUNT, 0, 0L)

    '     (int)SNDMSG((hwnd), TCM_GETCURFOCUS, 0, 0)

    '     SNDMSG((hwnd),TCM_SETCURFOCUS, i, 0)

    '     (int)SNDMSG((hwnd), TCM_SETMINTABWIDTH, 0, x)

    '     (void)SNDMSG((hwnd), TCM_DESELECTALL, fExcludeFocus, 0)

    '     (BOOL)SNDMSG((hwnd), TCM_HIGHLIGHTITEM, (WPARAM)i, (LPARAM)MAKELONG (fHighlight, 0))

    '     (DWORD)SNDMSG((hwnd), TCM_SETEXTENDEDSTYLE, 0, dw)

    '     (DWORD)SNDMSG((hwnd), TCM_GETEXTENDEDSTYLE, 0, 0)

     if (m.Msg == Win32.WM_ACTIVATE && m.HWnd == f.Handle

        public const int ERROR_HWNDS_HAVE_DIFF_PARENT = 1441;

        public const int OLE_E_INVALIDHWND = (int)(0x8004000F - 0x100000000);

        public const int DRAGDROP_E_INVALIDHWND = (int)(0x80040102 - 0x100000000);

        public const int OLEOBJ_S_INVALIDHWND = 0x00040182;

     int AddDesktopItemWithUI(IntPtr hwnd, ref COMPONENT pcomp, DtiAddUI dwFlags);

     int AddUrl(IntPtr hwnd, [MarshalAs(UnmanagedType.LPWStr)] string pszSource, ref COMPONENT pcomp, AddURL dwFlags);

    Function AddDesktopItemWithUI(ByVal hwnd As IntPtr, ByRef pcomp As COMPONENT, ByVal dwFlags As DtiAddUI) As Integer

    Function AddUrl(ByVal hwnd As IntPtr, <MarshalAs(UnmanagedType.LPWStr)> ByVal pszSource As String, ByRef pcomp As COMPONENT, ByVal dwFlags As AddURL) As Integer

   void Authenticate(IntPtr phwnd,

   Sub Authenticate(IntPtr phwnd,

    /// <param name="phwnd">The HWND of the parent window for a default user interface.</param>

    ///Client should also set phwnd to zero.</param>

    public void Authenticate(IntPtr phwnd, ref string pszUsername, ref string pszPassword)

        phwnd = IntPtr.Zero;

        IntPtr hwndEdit,

        int GetWindow(out IntPtr phwnd);

    Public Overridable Sub GetWindow(ByRef phwnd As System.IntPtr) Implements IDeskBand.GetWindow, IDockingWindow.GetWindow, IOleWindow.GetWindow

    phwnd = Handle

    Sub GetWindow(ByRef phwnd As System.IntPtr)

    Sub GetWindow(ByRef phwnd As System.IntPtr)

    Sub GetWindow(ByRef phwnd As System.IntPtr)

    Public hwnd As IntPtr

        int GetWindow(out IntPtr phwnd);

    Public Overridable Sub GetWindow(ByRef phwnd As System.IntPtr) Implements IDeskBand.GetWindow, IDockingWindow.GetWindow, IOleWindow.GetWindow

    phwnd = Handle

    Sub GetWindow(ByRef phwnd As System.IntPtr)

    Sub GetWindow(ByRef phwnd As System.IntPtr)

    Sub GetWindow(ByRef phwnd As System.IntPtr)

    Public hwnd As IntPtr

     uint ShowMessage(IntPtr hwnd,

     uint ShowHelp(IntPtr hwnd, [MarshalAs(UnmanagedType.LPWStr)] string pszHelpFile,

    Function ShowMessage(ByVal hwnd As IntPtr, <MarshalAs(UnmanagedType.LPWStr)> ByVal lpstrText As String, <MarshalAs(UnmanagedType.LPWStr)> ByVal lpstrCaption As String, ByVal dwType As Integer, <MarshalAs(UnmanagedType.LPWStr)> ByVal lpstrHelpFile As String, ByVal dwHelpContext As Integer, ByRef lpResult As Integer) As Integer

    Function ShowHelp(ByVal hwnd As IntPtr, <MarshalAs(UnmanagedType.LPWStr)> ByVal pszHelpFile As String, ByVal uCommand As Integer, ByVal dwData As Integer, ByVal ptMouse As tagPoint, <MarshalAs(UnmanagedType.IDispatch)> ByVal pDispatchObjectHit As Object) As Integer

        [In] IntPtr hwnd,

    void DragEnter([In] IntPtr hwndTarget, [In, MarshalAs(UnmanagedType.Interface)] IDataObject_Com dataObject, [In] ref drawing.Point pt, [In] DragDropEffects effect);

        dropHelper.DragEnter(hWnd, e.Data as IDataObject_Com, ref point, e.Effects);

                   [In, ComAliasName ( "ShellObjects.wireHWND" )] ref IntPtr hwnd,

             HandleRef hwndParent,

             ByVal hwndParent As IntPtr,

    void Redirect ( [In] ref Guid rfid, [In] IntPtr hwnd, [In] uint Flags,

    void Redirect ( [In] ref Guid rfid, [In] IntPtr hwnd, [In] uint Flags,

     void DoVerb(uint iVerb, uint lpmsg, object pActiveSite, uint lindex, uint hwndParent, uint lprcPosRect);

    /// <param name="phwnd">Pointer to where to return the window handle.</param>

    void GetWindow (out IntPtr phwnd) ;

      ''' <param name="phwnd">Pointer to where to return the window handle.</param>

      Sub GetWindow(<System.Runtime.InteropServices.Out()> ByRef phwnd As IntPtr)

        /// <param name="hwndParent">A handle to the dialog box's parent window.</param>

            IntPtr hwndParent, //HWND

    void GetWindow(out IntPtr phwnd);

    /// <param name="hwnd">Optional window handle</param>

    void ParseDisplayName(IntPtr hwnd, IntPtr pbc, String pszDisplayName, UInt32 pchEaten, out IntPtr ppidl, UInt32 pdwAttributes);

    /// <param name="hwnd">If user input is required to perform the enumeration, this window handle should be used by the enumeration object as the parent window to take user input.</param>

    void EnumObjects(IntPtr hwnd, ESHCONTF grfFlags, out IntPtr ppenumIDList);

    /// <param name="hwndOwner">Handle to the owner window.</param>

    void CreateViewObject(IntPtr hwndOwner, [In] ref Guid riid, out IntPtr ppv);

    /// <param name="hwndOwner">Handle to the owner window that the client should specify if it displays a dialog box or message box.</param>

    void GetUIObjectOf(IntPtr hwndOwner, UInt32 cidl, [MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 1)]IntPtr[] apidl, [In] ref Guid riid, UInt32 rgfReserved, out IntPtr ppv);

    /// <param name="hwnd"> Handle to the owner window of any dialog or message boxes that the client displays.</param>

    void SetNameOf(IntPtr hwnd, IntPtr pidl, String pszName, ESHCONTF uFlags, out IntPtr ppidlOut);

    void Resolve(IntPtr hwnd, UnsafeNativeMethods.SLR_FLAGS fFlags);

    Sub Resolve(ByVal hWnd As IntPtr, ByVal fFlags As UInteger)

    void Resolve(IntPtr hwnd, UnsafeNativeMethods.SLR_FLAGS fFlags);

    <PreserveSig()> Function Resolve(ByVal hwnd As IntPtr, ByVal fFlags As Integer) As HRESULT

        [Out] out UInt32 phWnd);

        [Out] out UInt32 phWnd);

      ///    /* [in] */ HWND hwnd,

      int AdviseEventSink(IUnknown pSink, IntPtr hwnd, uint dwFlags, ref uint pdwCookie);

    int HWND { [MethodImpl(MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime), DispId(-515)] get; }

    int HWND { [MethodImpl(MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime), DispId(-515)] get; }

    ReadOnly Property HWND() As Integer

    int HWND { [MethodImpl(MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime), DispId(-515)] get; }

    int HWND { [MethodImpl(MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime), DispId(-515)] get; }

    ReadOnly Property HWND() As Integer

        [In] IntPtr hwndParent,

        [In] IntPtr hwndParent,

        [In] IntPtr hwndParent,

        [In] IntPtr hwndParent,

    /// <summary>The progress dialog box will be modal to the window specified by hwndParent. By default, a progress dialog box is modeless.</summary>

    ''' <summary>The progress dialog box will be modal to the window specified by hwndParent. By default, a progress dialog box is modeless.</summary>

static extern bool AddClipboardFormatListener(IntPtr hwnd);

Public Function AddClipboardFormatListener(hWnd As IntPtr) As <MarshalAs(UnmanagedType.Bool)>Boolean

Declare Function AddClipboardFormatListener Lib "user32.dll" (hWnd As Long) As Boolean

static extern bool AnimateWindow(IntPtr hwnd, int time, AnimateWindowFlags flags);

Shared Function AnimateWindow(ByVal hwnd As IntPtr, ByVal time As Integer, ByVal flags As AnimateWindowFlags) As Boolean

    Private Shared Function GetSystemMenu(ByVal hWnd As IntPtr, ByVal bRevert As Boolean) As IntPtr

static extern uint ArrangeIconicWindows(IntPtr hWnd);

static extern IntPtr BeginPaint(IntPtr hwnd, out PAINTSTRUCT lpPaint);

Public Shared Function BeginPaint(ByVal hwnd As IntPtr, <Out()> ByRef lpPaint As PAINTSTRUCT) As IntPtr

static extern bool BringWindowToTop(IntPtr hWnd);

static extern bool BringWindowToTop(HandleRef hWnd);

Private Shared Function BringWindowToTop(ByVal hwnd As IntPtr) As Boolean

Public Declare Function BringWindowToTop Lib "user32" (ByVal HWnd As IntPtr) As Boolean

static extern IntPtr CallWindowProc(WndProcDelegate lpPrevWndFunc, IntPtr hWnd, uint Msg, IntPtr wParam, IntPtr lParam);

Private Shared Function CallWindowProc(lpPrevWndFunc As WndProcDelegate, hWnd As IntPtr, Msg As UInteger, wParam As IntPtr, lParam As IntPtr) As IntPtr

static extern ushort CascadeWindows(IntPtr hwndParent, uint wHow,

static extern bool ChangeClipboardChain(IntPtr hWndRemove, IntPtr hWndNewNext);

static extern DISP_CHANGE ChangeDisplaySettingsEx(string lpszDeviceName, ref DEVMODE lpDevMode, IntPtr hwnd, ChangeDisplaySettingsFlags dwflags, IntPtr lParam);

Private Shared Function ChangeDisplaySettingsEx(ByVal lpszDeviceName As String, ByRef lpDevMode As DEVMODE, ByVal hwnd As IntPtr, ByVal dwflags As UInteger, ByVal lParam As IntPtr) As DISP_CHANGE

public static extern bool ChangeWindowMessageFilterEx(IntPtr hWnd, uint msg, ChangeWindowMessageFilterExAction action,ref CHANGEFILTERSTRUCT changeInfo);

Private Shared Function ChangeWindowMessageFilterEx(hWnd As IntPtr, msg As UInteger, action As ChangeWindowMessageFilterExAction, ByRef changeInfo As CHANGEFILTERSTRUCT) As <MarshalAs(UnmanagedType.Bool)> Boolean

static extern IntPtr ChildWindowFromPointEx(IntPtr hWndParent, Point pt, uint uFlags);

Public Function ChildWindowFromPointEx(ByVal hWndParent As IntPtr, ByVal P As POINTAPI, ByVal uFlags As CWPFlags) As IntPtr

static extern IntPtr ChildWindowFromPointEx(IntPtr hWndParent, Point pt, uint uFlags);

Public Function ChildWindowFromPointEx(ByVal hWndParent As IntPtr, ByVal P As POINTAPI, ByVal uFlags As CWPFlags) As IntPtr

static extern bool ClientToScreen(IntPtr hWnd, ref Point lpPoint);

Private Shared Function ClientToScreen(ByVal hWnd As IntPtr, ByRef lpPoint As Point) As Boolean

    static extern bool ClientToScreen(IntPtr hwnd, ref Point lpPoint);

static extern int CloseWindow (IntPtr hWnd);

static extern bool CreateCaret(IntPtr hWnd, IntPtr hBitmap, int nWidth,

    Public Shared Function CreateCaret(ByVal hWnd As IntPtr, ByVal hBitmap As IntPtr, ByVal nWidth As Integer, ByVal nHeight As Integer) As Boolean

    Public Shared Function CreateCaret(ByVal hWnd As IntPtr, ByVal hBitmap As IntPtr, ByVal nWidth As Integer, ByVal nHeight As Integer) As Boolean

    IntPtr hwndParent,

/// <param name="nHeight">Specifies the height, in device units, of the window. For overlapped windows, nHeight is the window's height, in screen coordinates. If the nWidth parameter is set to CW_USEDEFAULT, the system ignores nHeight.</param> <param name="hWndParent">Handle to the parent or owner window of the window being created. To create a child window or an owned window, supply a valid window handle. This parameter is optional for pop-up windows.

/// <para>Windows 2000/XP: To create a message-only window, supply HWND_MESSAGE or a handle to an existing message-only window.</para></param>

   IntPtr hWndParent,

''' <param name="nHeight">Specifies the height, in device units, of the window. For overlapped windows, nHeight is the window's height, in screen coordinates. If the nWidth parameter is set to CW_USEDEFAULT, the system ignores nHeight.</param> <param name="hWndParent">Handle to the parent or owner window of the window being created. To create a child window or an owned window, supply a valid window handle. This parameter is optional for pop-up windows.

''' <para>Windows 2000/XP: To create a message-only window, supply HWND_MESSAGE or a handle to an existing message-only window.</para></param>

     ByVal hWndParent As IntPtr, _

            wndclass.lpfnWndProc = (WndProc)((hWnd, message, wParam, lParam ) => {

                        hdc = Win32.BeginPaint (hWnd, out ps) ;

                        Win32.GetClientRect (hWnd, out rect) ;

                        Win32.EndPaint(hWnd, ref ps);

                return Win32.DefWindowProc(hWnd, (WM)message, wParam, lParam);

            IntPtr hwnd = Win32.CreateWindowEx(

            if( hwnd == IntPtr.Zero )

            Win32.ShowWindow(hwnd, ShowWindowCommands.Normal );

            Win32.UpdateWindow(hwnd);

    ///<Summary>Does not activate the window. If this flag is not set, the window is activated and moved to the top of either the topmost or non-topmost group (depending on the setting of the hWndInsertAfter parameter).</Summary>

    ///<Summary>Retains the current Z order (ignores the hWndInsertAfter parameter).</Summary>

    '''<Summary>Does not activate the window. If this flag is not set, the window is activated and moved to the top of either the topmost or non-topmost group (depending on the setting of the hWndInsertAfter parameter).</Summary>

    '''<Summary>Retains the current Z order (ignores the hWndInsertAfter parameter).</Summary>