Finally, for scenarios where an API will be targeting one specific window to which it will send messages, the MesssageEvents class exposes the handle for the underlying window used by MessageEvents to receive and process events. That underlying window is created by MessageEvents. MessageWindow, shown in Figure 1 , is a private nested type within MessageEvents. The class also overrides the WndProc method, which is the method executed in response to the window receiving a message.
The override checks to see whether the received message is in the message set, and thus whether it is one previously registered for an event to be raised.
If it is, WndProc raises the MessageReceived event. There are several interesting things to note about how this event is raised. This is because of a trick played by the C compiler. When I declared the MessageReceived event, I was really doing two things: declaring a public event and declaring a private delegate. The public event provides add and remove accessors, which is why any class is able to register and unregister handlers with the event.
However, because MessageWindow is a nested class within MessageEvents, MessageWindow does have access to the private implementation details of MessageEvents. In this case, that allows MessageWindow access to the private MessageReceived delegate, allowing it to be invoked directly by MessageWindow. The SynchronizationContext is used to raise the event through an asynchronous Post rather than a synchronous Send in the synchronization context of the application, whatever that may be.
In a console application, SynchronizationContext. Post simply executes the delegate on a ThreadPool thread. Post executes the delegate by marshaling its invocation back to the UI thread. For more information on SynchronizationContext, see msdn. To solve this problem, Windows uses a message-passing model.
The operating system communicates with your application window by passing messages to it. A message is simply a numeric code that designates a particular event. For example, if the user presses the left mouse button, the window receives a message that has the following message code.
Some messages have data associated with them. To pass a message to a window, the operating system calls the window procedure registered for that window. And now you know what the window procedure is for. An application will receive thousands of messages while it runs.
Consider that every keystroke and mouse-button click generates a message. Additionally, an application can have several windows, each with its own window procedure. How does the program receive all these messages and deliver them to the correct window procedure? The application needs a loop to retrieve the messages and dispatch them to the correct windows.
For each thread that creates a window, the operating system creates a queue for window messages. This queue holds messages for all the windows that are created on that thread. The queue itself is hidden from your program. You cannot manipulate the queue directly. However, you can pull a message from the queue by calling the GetMessage function. But the checked event get called and the checkmark blinks inside the square box so I really think it sucks hard time. It seems to be the perfect way to do so, but I don't know how to make this work.
I tried to read a bit about notifications, messages, etc but found nothing understable enough for me to apply it to my code. Simply implement the ItemCheck event. You can cancel the check by changing the e. NewValue property. A silly example:. Stack Overflow for Teams — Collaborate and share knowledge with a private group.
Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. How to handle Windows Messages Ask Question. Messaging; using System. Message ; msg. GetType ; msgQ. Body ; lblDetails. Button ; this. Label ; this. Point , 61 ; this. Size , 33 ; this. EventHandler this. Point , ; this. Size , 31 ; this. Size 0, 13 ; this. SizeF 6 F, 13 F ; this. Font; this. Size , ; this. Add this.
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