I am using a third-party Windows Forms control that performs some actions "delayed" using the Application.Idle event.
Now that we're moving our application to WPF, these actions stopped working.
I've found that the System.Windows.Forms.Application.Idle event is not raised as expected.
How can I get the Idle event to fire in a WPF application so that I can continue to use that third-party control (within a WindowsFormsHost)? It is not possible to modify the Windows Forms control.
You should read this page on MSDN which describes the message loop behavior in a WPF application. In particular it looks like the ComponentDispatcher class can be used to catch a ThreadIdle event which would roughly correspond to the Windows Forms Application.Idle event.
You could then presumably use the System.Windows.Forms.Application.RaiseIdle method to raise the Idle event as the component expects.
If you are using a WPF Application, you are actually no longer using the System.Windows.Forms.Application class to run your application, even if your application contains a Windows Forms Control.
Instead, you are using the System.Windows.Application class (different namespace).
Related
I have been developing a Lync Silverlight application in Silverlight and now I am trying to shift it to WPF.
However, I am facing some thread affinity issues. For example I display the Lync client's state on my page in a textblock, and so in my code behind have wired a state changed event handler, that writes the new state into the textblock whenever the state of Lync client changes.
Now, this worked perfectly in silverlight but seemingly is not allowed in WPF.
Now my questions are:
How come it works in Silverlight bt not in WPF, even though Silverlight is supposed to be a subset of WPF?
Thread affinity is an important concept and I know we can use invoke dispatcher, but doesn't it just beat the concept of asynchronous programming in form of event handlers and callbacks?
I have a button defined in my XAML page, and the click event handler defined on it can access other UI elements, it does not suffer the problem outlined above.
But if I define a LyncClient instance in my code-behind, event handlers defined on it cannot access the UI elements. Why so, I detected no such difference between UIElements and other objects in Silverlight?
Based on above comments, I'll suggest the following "answer"...
I would guess it is more likely than not that there is some sort of different in the way that the SL API was written than that of the WPF api. That could explain the difference in the thread that is used when the API issues the callback. To verify this, you could:
Ask MS directly
Put some diagnostics code in your callback method to log the thread ID and compare that to the main thread of the application. Do this for both SL and WPF to see if they are the same or different threads.
Open the assemblies in Reflector to inspect how each API was written.
In terms of handling this specific situation, in your callback, you could:
Get the dispatcher object (different for SL than WPF) and always issue UI updates through Dispatcher.Invoke.
Use databinding and INotifyPropertyChanged to insulate the UI from the property. You could delcare a property on a ViewModel or in the code behind. Then bind the UI's textbox to that property. Databinding has some smarts in it that will automatically marshal property changes to the correct thread (in most cases anyway).
Hope that helps.
I have what, on the face of it, seems to be a really simple requirement - to be able to show a messagebox from within the view model of my WPF prism application.
Reading the documentation everything sounds good when I'm reading about Interaction Requests but I then find out that WPF doesn't support PopupChildWindowAction.
How are people getting around this. Basically I want a Messagebox in my shell module / or a infrastructure module that will subscribe to events and popup when that event is published.
Another issue I had was I want the popup to be centered on the parent window (the shell).
Just wondered how other people approached this. There seem to be a number of different ways to go but neither seem to fit the bill exactly.
From A CodePlex post by Karl Shifflet:
I've written a WPF version of the Interaction Request for my the Box MVVM Training here:
http://visualstudiogallery.msdn.microsoft.com/en-us/3ab5f02f-0c54-453c-b437-8e8d57eb9942
Install this Visual Studio Extension.
Create a new project with the MVVM Training Template.
Check out DialogInteractionRequestView.xaml and its implementation.
Cheers,
Karl
Use the RegionPopupBehavior from Prism 2.2 RI.
Use the EventAggregator in PRISM to subscribe to events, and have an in-memory presenter that listens for an event and then creates a view using the event data and calls ShowDialog on the view.
The dialog result can then be used to publish a 'response' event that would be routed back to the process that initiated the event that resulted in the display of the dialog.
Since PopupChildWindowAction is only in Silverlight, I have created my own PopupAction by inheriting from TriggerAction class and simply overridden body of Invoke() method to bring up a PopupWindow where I can pass any UserControl from xaml within the prism interaction trigger tag. From within ViewModel I am raising interactivity request event which triggers my PopupAction in view and opens the popup with desired user control being displayed onto it. Seems to work. I'll need to polish the example more. But here is a link -
http://wpfgrid.blogspot.com/2013/01/simple-prism-mvvm-way-to-display-dialog.html#step3
i have created one component in WPF. its working fine with WPF but when i tried to use it in windows application i am getting one issue.
i have one textbox in that control so in when the control hosted in windows applicaion and i try to type something in that textbox its not working.
i tried to put some messageboxes in "KeyPreview", "KeyDown" and "Textxchanged" events any of these events have not been fired.
so is there any limitation for WPF usercontrols usage in windows application??
one more thing i have used Dispatcher timer in the usercontrol.
This MSDN walkthrough shows how to use a WPF user control in Windows Forms. It may help you in your query.
http://msdn.microsoft.com/en-us/library/ms745781.aspx
so i came across this interesting article on WPF exception handling:
http://srtsolutions.com/public/item/251263
it works by declaring DispatcherUnhandledException handler in xaml <application> node.
but what if a WPF window is launched from win forms application?
where can i declare a general exception handler?
The problem is that when WPF crashes, it brings down the whole WinForms app with it.
*Edit
what if instead of launching the WPF window directly, i launched an "Application" which than defined a start window?? is that possible/advisable?
Attach your handler to the <obj>.Dispatcher.UnhandledException event, where <obj> is any WPF control, or another DispatcherObject that is created on the same thread.
I believe the traditional "global" exception handlers for Windows Forms would apply here:
Hook the thread exception as the first line in Main:
Application.ThreadException += new ThreadExceptionEventHandler(new ThreadExceptionHandler().ApplicationThreadException);
I'm building a custom Silverlight UserControl which needs to listen to events using Preview/Tunneling, but for some reason the compiler is telling me they are not recognized or accessible.
For example, I can add an event handler to MouseLeftButtonDown, but not PreviewMouseLeftButtonDown. This doesn't make sense because according to Microsoft (http://msdn.microsoft.com/en-us/library/system.windows.uielement_members(v=VS.100).aspx) all UIElements should have Preview events attached.
Any ideas as to why this is happening? I'm using Visual Studio 2010 Trial, Blend 4 RC and .Net 4, if that makes a difference.
Silverlight does not support preview events nor does it support routed events (bubbling/tunneling) except for a few core events.
If you are trying to create a control that works with both WPF and Silverlight, you will need to take a different approach. Depending on what you're trying to do, you may be able to accomplish what you want by rigging up a handler in code and specifying that you want handled events too.
// the last parameter indicates we want to receive events that
// were marked as e.Handled = true by other listeners
// this type of event handler can only be done in code
myUserControl.AddHandler(
UIElement.MouseLeftButtonDownEvent,
OnMouseLeftButtonDown,
true
);
You're looking at the help for WPF, not Silverlight. Silverlight is (mostly) a subset of WPF, and much of the functionality is missing.
The Silverlight UIElement help does not show those events, as they do not exist in Silverlight.