Specifies a notification method that is called when the handle for a window is changed.
Assembly: System.Windows.Forms (in System.Windows.Forms.dll)
This method is invoked when the value of the Handle property has changed.Notes to Inheritors:
Override this method to track changes that are made to the window handle.
The following code example demonstrates creating a window with a specific operating system window class name. The example creates a class that inherits from NativeWindow to accomplish this. The example also demonstrates overriding the method to be notified when the Handle changes.
The MyNativeWindow class creates a new window with the ClassName set to BUTTON. This creates a Win32 button window. The location and size of the button is set, along with specifying additional window styles. The class demonstrates how to use the CreateHandle method and override the WndProc method to intercept window messages that are received. Although the example looks for the WM_ACTIVATEAPP message, this can be replaced in a real program with window messages specific to the type created.
Some control types send their window messages to the window parent instead of the window. See the Windows Platform SDK for more information.
' MyNativeWindow class to create a window given a class name. <System.Security.Permissions.PermissionSetAttribute(System.Security.Permissions.SecurityAction.Demand, Name:="FullTrust")> _ Friend Class MyNativeWindow Inherits NativeWindow ' Constant values were found in the "windows.h" header file. Private Const WS_CHILD As Integer = &H40000000, _ WS_VISIBLE As Integer = &H10000000, _ WM_ACTIVATEAPP As Integer = &H1C Private windowHandle As Integer Public Sub New(ByVal parent As Form) Dim cp As CreateParams = New CreateParams() ' Fill in the CreateParams details. cp.Caption = "Click here" cp.ClassName = "Button" ' Set the position on the form cp.X = 100 cp.Y = 100 cp.Height = 100 cp.Width = 100 ' Specify the form as the parent. cp.Parent = parent.Handle ' Create as a child of the specified parent cp.Style = WS_CHILD Or WS_VISIBLE ' Create the actual window Me.CreateHandle(cp) End Sub ' Listen to when the handle changes to keep the variable in sync <System.Security.Permissions.PermissionSetAttribute(System.Security.Permissions.SecurityAction.Demand, Name:="FullTrust")> _ Protected Overrides Sub OnHandleChange() windowHandle = Me.Handle.ToInt32() End Sub <System.Security.Permissions.PermissionSetAttribute(System.Security.Permissions.SecurityAction.Demand, Name:="FullTrust")> _ Protected Overrides Sub WndProc(ByRef m As Message) ' Listen for messages that are sent to the button window. Some messages are sent ' to the parent window instead of the button's window. Select Case (m.Msg) Case WM_ACTIVATEAPP ' Do something here in response to messages End Select MyBase.WndProc(m) End Sub End Class
Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98
The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.