Creates a window and its handle with the specified creation parameters.
Assembly: System.Windows.Forms (in System.Windows.Forms.dll)
The operating system ran out of resources when trying to create the native window.
The native Win32 API could not create the specified window.
The cp parameter specifies the values that are passed to the native Win32 CreateWindowEx method to create a window and its handle.
When the ClassName field is not Nothing, the newly created window handle inherits from the specified class. For example, if ClassName is set to BUTTON, the newly created window is based on the Win32 BUTTON window class. The Param property of the ClassName object must either be Nothing or reference an instance of a class that was declared as a structure.
The class name provided is registered with the operating system.
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 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 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
for safe subwindows to call this method. Associated enumeration: UIPermissionWindow.SafeSubWindows
to create a top-level window. This permission is only demanded if the window style is not a child or if the window does not have a parent. Associated enumeration: UIPermissionWindow.SafeTopLevelWindows