如何在用户控件中拦截父窗体的 wndproc

Question

Is there method for receive wndproc of parent form in user control?

I'm making titlebar user control and I want to receive windows message about form resize.

(this form is formborderstyle=none.)

Answer 1

Since the WndProc function doesn't intercept all windows messages I got used to create a MessageFilter , since this one does filter every windows message. So at first you create a new class which will implement the interface IMessageFilter .

class MessageFilter : IMessageFilter
{
    public static IntPtr MyHandle { get; set; }

    public bool PreFilterMessage(ref Message m)
    {
        if (m.Msg == /*windows code for resizing*/ && m.HWnd == MyHandle)
        {
            //do what you desire
            return true;
        }
        else
            return false;
    }
}

So you filter all messages and wait until the message contains the code for resizing and that the code aims to your specific window. In Windows all controls like a button, form, ... have a handle, which is unique. The handle is used to tell to which specific control the windows message shell be send, so we can use this as a criterion for the resize detection.

MyHandle shell contain the window handle of your form you want to listen to it's resizing. So you should set it eg in the constructor:

MessageFilter.MyHandle = this.Handle;

Now we created our own MessageFilter , now we have to add it to your application that it listens to the windows messages. This should be set in the constructor.

MessageFilter msgFilter = new MessageFilter();

Application.AddMessageFilter(msgFilter);