Practical tips for using Sendmessage_ in C #

In C #, the program uses a driver that is event driven instead of the original message driver. Although the. NET Framework provides a rich range of events, the rich message defined in the previous system provides a convenient way of implementing system programming, so using messages in C # sometimes greatly improves programming efficiency.

1 definition messages

In C # The message needs to be defined as the original 16-digit number in the Windows system, such as

const int Wm_lbutton = 0x201; The left click message of the mouse is defined

public const INT user = 0X0400//is a Windows system-defined user message

2 message sending

Message sending is implemented through the API function SendMessage provided by Windows, and its prototype is defined as

[DllImport ("User32.dll", entrypoint= "SendMessage")]

private static extern int SendMessage (

int hWnd,//Handle to Destination window

int MSG,//message

int WParam,///parameter

int LParam//second message parameter

);

3 Acceptance of the message

In C #, any window has a receive processing function that is also a message, which is the Defproc function

You can overload the function in form to process messages

protected override void Defwndproc (ref System.WinForms.Message m)

{

Switch (m.msg)

{

Case Wm_lbutton:

String differs from the use of the format function for CString in MFC

String message = String. Format (Receive Message! parameter is: {0},{1} ", M.wparam,m.lparam);

MessageBox.Show (message);///Display a messages box

Break

Default

Base. Defwndproc (ref m);///calls the base class function to handle non custom messages.

Break

}

}

In fact, events in C # are also implemented by encapsulating system messages, if you do not handle that in the Defwndproc function

So, he'll hand it over to the system to process the message, and the system will implement the mouse-click processing function through the proxy, so you can

Defproc function to intercept a message, such as a click message that you want to intercept a button

4 other message processing methods in C #

In C # There are times when you need to preprocess the message of a control, such as if you're working with an Excel file with a OWC Spreedsheet control, and you don't want the user to randomly select

Data to edit, you can screen out mouse events, this time you must intercept the system predefined events (this is called Subclasses in MFC), you can provide through C # an interface

IMessageFilter to implement the filtering of messages

public class Form1:system.windows.forms.form,imessagefilter

{

const int WM_MOUSEMOVE = 0x200

public bool Prefiltermessage (ref message M)

{Keys keycode = (keys) (int) M.wparam & Keys.keycode;

if (m.msg = = m.msg==wm_mousemove)//| | M.msg = = Wm_lbuttondown

{

MessageBox.Show ("Ignoring Escape ...");

return true;

}

return false;

}

}