Use SendMessage in C #

In C #, the program adopts event-driven rather than the original message-driven driver, although. the. net Framework provides a wealth of events, but previously defined rich messages in the system provide a convenient way to program the system, therefore, using messages in C # can greatly improve programming efficiency.

1. Define a message

In c #, the message must be defined as the original hexadecimal number in windows, such

Const int WM_Lbutton = 0x201; // defines the left-click message of the mouse

Public const int USER = 0x0400 // is a USER message defined by windows.

2 Message sending

Message sending is implemented through the API function SendMessage provided by windows. Its prototype is defined

[DllImport ("User32.dll", EntryPoint = "SendMessage")]
Private static extern int SendMessage (
Int hWnd, // handle to destination window
Int Msg, // message
Int wParam, // first message parameter
Int lParam // second message parameter
);

3. Message acceptance

In C #, any window has a message receiving and processing function, that is, the defproc function.

You can reload this function in form to process messages.

Protected override void DefWndProc (ref System. WinForms. Message m)
{
Switch (m. msg)
{
Case WM_Lbutton:
/// The Format function of string and CString in MFC is used differently.
String message = string. Format ("message received! Parameter: {0}, {1} ", m. wParam, m. lParam );
MessageBox. Show (message); // display a message box
Break;
Default:
Base. DefWndProc (ref m); // call the base class function to process non-custom messages.
Break;
}