{"id":3671,"date":"2013-11-12T13:57:53","date_gmt":"2013-11-12T08:27:53","guid":{"rendered":"http:\/\/live-42gears-site.pantheonsite.io\/blog\/?p=3671"},"modified":"2023-01-13T06:02:23","modified_gmt":"2023-01-13T06:02:23","slug":"sub-classing-a-wpf-applications-wndproc","status":"publish","type":"post","link":"https:\/\/www.42gears.com\/es\/blog\/sub-classing-a-wpf-applications-wndproc\/","title":{"rendered":"Sub Classing a WPF Application\u2019s WndProc"},"content":{"rendered":"\n\n\n\n\n
Applies to<\/span>:<\/strong><\/span><\/td>\n<\/tr>\n
Product<\/strong><\/span><\/td>\nGeneral<\/span><\/strong><\/td>\n<\/tr>\n
Platform<\/strong><\/span><\/td>\nWindows<\/span><\/strong><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

With the introduction of Windows Presentation Foundation<\/em> (WPF), developers can now create rich User Interface applications which is preferred by end users. While developing such applications, sometimes there can be a need to intercept the Window messages. This can be achieved easily in Win32 and WinForm applications and one would wonder is this possible in WPF as well? The answer to this question is, yes it is possible. This article does exactly that and will explain how to Sub class a WPF application\u2019s WndProc.<\/p>\n

.Net Classes Used<\/span><\/strong><\/p>\n

    \n
  1. WindowInteropHelper <\/strong>: This class is needed to retrieve the handle of the WPF application window.<\/li>\n
  2. HwndSource <\/strong>: The class will provide a method to hook the WndProc of the WPF application.<\/li>\n<\/ol>\n

    Code Snippet<\/span><\/strong><\/p>\n

    \n

    private void MainWindowLoaded(object sender, RoutedEventArgs e)<\/p>\n

    {
    \nHwndSource source = HwndSource.FromHwnd(new WindowInteropHelper(this).Handle);
    \nsource.AddHook(new HwndSourceHook(WndProc));
    \n}<\/p>\n

    private IntPtr WndProc(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam,ref bool handled)
    \n{
    \nif(msg==WM_CLOSE)
    \n{
    \n\/\/Avoiding a close event
    \nhandled=true;
    \n}
    \nreturn IntPtr.Zero;
    \n}<\/p>\n<\/div>\n

    In the above Snippet, the WindowInteropHelper<\/em> class provides the handle to the WPF application window which is passed to the HwndSource<\/em> class and the AddHook<\/em> method allows to intercept the Window messages using a WndProc, which is WM_CLOSE in this case<\/p>\n

    NOTE: The HwndSource object should be created only in the Loaded event of your application because that\u2019s when your WPF application is assigned a Window handle, else the WindowInteropHelper class will return an invalid handle.<\/strong><\/p>\n

    Download Source Files<\/span><\/strong><\/p>\n

    \"\"<\/a><\/p>\n

    Read more about our products:<\/strong><\/p>\n

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    Applies to: Product General Platform Windows With the introduction of Windows Presentation Foundation (WPF), developers can now create rich User Interface applications which is preferred by end users. While developing such applications, sometimes there can be a need to intercept the Window messages. This can be achieved easily in Win32 and WinForm applications and one…<\/p>\n","protected":false},"author":7,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[39,8,97,98,31,60],"tags":[182,27],"class_list":["post-3671","post","type-post","status-publish","format-standard","hentry","category-development","category-general","category-windows-7","category-windows-8","category-windows-mobile","category-windows-phone-7","tag-general-2","tag-windows"],"acf":[],"yoast_head":"\nSub Classing A WPF Application\u2019s WndProc | 42Gears<\/title>\n<meta name=\"description\" content=\"42Gears\u2019 blog has everything you need to future-proof your business. 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