直击本质：WPF 框架是如何实现模态窗口的

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public Nullable<bool> ShowDialog() { // NOTE: // _threadWindowHandles is created here. This reference is nulled out in EnableThreadWindows // when it is called with a true parameter. Please do not null it out anywhere else. // EnableThreadWindow(true) is called when dialog is going away. Once dialog is closed and // thread windows have been enabled, then there no need to keep the array list around. // Please see BUG 929740 before making any changes to how _threadWindowHandles works. _threadWindowHandles = new ArrayList(); //Get visible and enabled windows in the thread // If the callback function returns true for all windows in the thread, the return value is true. // If the callback function returns false on any enumerated window, or if there are no windows // found in the thread, the return value is false. // No need for use to actually check the return value. UnsafeNativeMethods.EnumThreadWindows(SafeNativeMethods.GetCurrentThreadId(), new NativeMethods.EnumThreadWindowsCallback(ThreadWindowsCallback), NativeMethods.NullHandleRef); //disable those windows EnableThreadWindows(false); try { _showingAsDialog = true; Show(); } catch { // NOTE: // See BUG 929740. // _threadWindowHandles is created before calling ShowDialog and is deleted in // EnableThreadWindows (when it's called with true). // // Window dlg = new Window(); // Button b = new button(); // b.OnClick += new ClickHandler(OnClick); // dlg.ShowDialog(); // // // void OnClick(...) // { // dlg.Close(); // throw new Exception(); // } // // // If above code is written, then we get inside this exception handler only after the dialog // is closed. In that case all the windows that we disabled before showing the dialog have already // been enabled and _threadWindowHandles set to null in EnableThreadWindows. Thus, we don't // need to do it again. // // In any other exception cases, we get in this handler before Dialog is closed and thus we do // need to enable all the disable windows. if (_threadWindowHandles != null) { // Some exception case. Re-enable the windows that were disabled EnableThreadWindows(true); } } }

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private object ShowHelper(object booleanBox) { try { // tell users we're going modal ComponentDispatcher.PushModal(); _dispatcherFrame = new DispatcherFrame(); Dispatcher.PushFrame(_dispatcherFrame); } finally { // tell users we're going non-modal ComponentDispatcher.PopModal(); } }