Message Structure
Implements a Windows message.
Assembly: System.Windows.Forms (in System.Windows.Forms.dll)
The Message type exposes the following members.
| Name | Description | |
|---|---|---|
![]() | HWnd | Gets or sets the window handle of the message. |
![]() | LParam | Specifies the LParam field of the message. |
![]() | Msg | Gets or sets the ID number for the message. |
![]() | Result | Specifies the value that is returned to Windows in response to handling the message. |
![]() | WParam | Gets or sets the WParam field of the message. |
| Name | Description | |
|---|---|---|
![]() ![]() | Create | Creates a new Message. |
![]() | Equals | Determines whether the specified object is equal to the current object. (Overrides ValueType::Equals(Object).) |
![]() | Finalize | Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.) |
![]() | GetHashCode | Returns the hash code for this instance. (Overrides ValueType::GetHashCode().) |
![]() | GetLParam | Gets the LParam value and converts the value to an object. |
![]() | GetType | Gets the Type of the current instance. (Inherited from Object.) |
![]() | MemberwiseClone | Creates a shallow copy of the current Object. (Inherited from Object.) |
![]() | ToString | Infrastructure. Returns a String that represents the current Message. (Overrides ValueType::ToString().) |
| Name | Description | |
|---|---|---|
![]() ![]() | Equality | Determines whether two instances of Message are equal. |
![]() ![]() | Inequality | Determines whether two instances of Message are not equal. |
The Message structure wraps messages that Windows sends. You can use this structure to wrap a message and assign it to the window procedure to be dispatched. You can also use this structure to get information about a message the system sends to your application or controls. For more information about Windows messages, see Messages and Message Queues.
You cannot create the Message directly. Instead, use the Create method. For the sake of efficiency, the Message uses its pool of existing Messages instead of instantiating a new one, if possible. However, if a Message is not available in the pool, a new one is instantiated.
The following code example demonstrates overriding the WndProc method to handle operating system messages identified in the Message. The WM_ACTIVATEAPP operating system message is handled in this example to know when another application is becoming active. For information about the available Message::Msg, Message::LParam, and Message::WParam values, see the MSG Structure documentation. For information about the actual constant values, see Message Constants.
using namespace System; using namespace System::Drawing; using namespace System::Windows::Forms; using namespace System::Security::Permissions; namespace csTempWindowsApplication1 { public ref class Form1: public System::Windows::Forms::Form { private: // Constant value was found in the "windows.h" header file. static const Int32 WM_ACTIVATEAPP = 0x001C; Boolean appActive; public: Form1() { appActive = true; this->Size = System::Drawing::Size( 300, 300 ); this->Text = "Form1"; this->Font = gcnew System::Drawing::Font( "Microsoft Sans Serif",18.0F,System::Drawing::FontStyle::Bold,System::Drawing::GraphicsUnit::Point,((System::Byte)(0)) ); } protected: virtual void OnPaint( PaintEventArgs^ e ) override { // Paint a string in different styles depending on whether the // application is active. if ( appActive ) { e->Graphics->FillRectangle( SystemBrushes::ActiveCaption, 20, 20, 260, 50 ); e->Graphics->DrawString( "Application is active", this->Font, SystemBrushes::ActiveCaptionText, 20, 20 ); } else { e->Graphics->FillRectangle( SystemBrushes::InactiveCaption, 20, 20, 260, 50 ); e->Graphics->DrawString( "Application is Inactive", this->Font, SystemBrushes::ActiveCaptionText, 20, 20 ); } } [SecurityPermission(SecurityAction::Demand, Flags=SecurityPermissionFlag::UnmanagedCode)] virtual void WndProc( Message% m ) override { // Listen for operating system messages. switch ( m.Msg ) { case WM_ACTIVATEAPP: // The WParam value identifies what is occurring. appActive = (int)m.WParam != 0; // Invalidate to get new text painted. this->Invalidate(); break; } Form::WndProc( m ); } }; } [STAThread] int main() { Application::Run( gcnew csTempWindowsApplication1::Form1 ); }
Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
