I have a silverlight application. When some action is executed, i want to show a wait cursor.
The problem is that i'm working with threads, and all my actions are executed in a thread.
So i have a threading helper that invokes and awaits all the threads - this works fine.
I need to access the main window element to change its cursor. How can i achieve this?
This:
ThreadingHelper.Invoke(() => App.Current.MainWindow.Content.Cursor = cursorStyle);
Throws me System.NotSupportedException: Out-of-browser specific settings do not affect in-browser applications.
How can i do the same for In-browser?
I have managed to get this working by this code:
ThreadingHelper.Invoke(() => {
var page = (MainPage)Application.Current.RootVisual;
page.Cursor = cursorStyle;
});
But maybe someone will offer more type-safe method?
Related
I have an app that launches a long update on the backend (Dynamics 365 in this case). I want to launch it in the background while the user can continue doing things.
The problem is that while this task is running, the other pages don't load when I click on them. Maybe is the usual behavior.
Tried with Task.Run() HostingEnvironment.QueueBackgroundWorkItem() and the result is the same.
This is how my controller looks like:
public ActionResult ConfirmCurrentMonthMeetings() {
//Task.Factory.StartNew(() => QueryHelper.MarkReadOnlyCurrentMonthMeetings(guide.Id, svc));
HostingEnvironment.QueueBackgroundWorkItem(clt => QueryHelper.MarkReadOnlyCurrentMonthMeetings(guide.Id, svc));
ViewBag.ConfirmingMeetingsMessage = "Meetings being confirmed on the background. This action might take a few minutes";
PrepareMainScreen();
return View("MainScreen");
}
Apparently the variable svc that I use to perform the queries to the CRM is a shared resource and cannot be used while it's in use. I defined a second one and worked fine.
Inside a UWP app I want to control some animations on a second screen from my main app window.
As far as I can tell I have two options: create a second Window or use the projection feature.
My questions are:
Which option would make more sense / would be easier to implement in this scenario?
How can I react to events from my main window on my second screen?
About Q2:
There are some way to interact with multi thread model. If you write your app based on the MultiView sample, you can use the SecondaryViewsHelper to call method on the another pages, etc. Or, you can call the LaunchUriAsync from each pages. If you regist your app as protocol handler, you can receive the call at OnLaunched method.
This is common for both Projection and Multi-View.
This SO page also helps you :)
Multiple instances of a Windows Universal App (Windows 10)
Edited: Sample - It's used on my uwp app - added.
// This is a method of Application class "F10Client".
// SecondaryViews is a member of this class.
// In my app, this method is called when the app resumes.
public async Task<bool> TogglePrivateMaskForAllPages(bool isMask)
{
bool retVal = true;
if (null != ((F10Client)F10Client.Current).SecondaryViews && 0 < ((F10Client)F10Client.Current).SecondaryViews.Count)
{
foreach (var view in ((F10Client)F10Client.Current).SecondaryViews)
{
// You should use dispatcher to call the page method.
await view.Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () =>
{
var thePage = (ImagePage)((Frame)Window.Current.Content).Content;
// calling the method.
thePage.TogglePrivacyMask(isMask);
});
}
}
return retVal;
}
For my first question, the Guidelines for projection manager helped me choose the right way to go:
Recently we came across some legacy WinForms application we needed to update with some new features. While expert testing the application, it was found that some old functionality is broken. Invalid cross-thread operation. Now before you take me for a newbie, I do have some experience with Windows Forms applications. I'm no expert, but I consider myself experienced with threading and know exactly how to manipulate GUI components from a worker thread.
Apparently the one who wrote this piece of software did not and just set UI control properties from a background thread. Of course it threw the usual exception, but it was encased in an all-catching try-catch block.
I spoke with a stakeholder to find out how long this functionality had been broken, and turned out it was fine before. I couldn't believe that, but he demoed me that the function actually works in PROD.
So our unrelated updates "broke" the software in three places, but I can't get my head around how it could have worked in the first place. According to source control, the bug has always been there.
Of course we updated the application with proper cross-thread UI handling logic, but now I'm in the unlucky position of having to explain to stakeholders with not much tech background why something that can't have worked like ever, did work fine until we did some unrelated changes to the system.
Any insights would be appreciated.
One more thing that came to mind: in two of the cases the background thread updated a ListView control that was on a non-selected (and thus non-displayed) TabPage control. The third time it was standard Label control (text property was set) that was initially empty and gets a Text assigned according to what the background thread finds.
Here's some code for you, very similar to the one we found:
private void form_Load(object sender, System.EventArgs e)
{
// unrelated stuff...
ThreadStart ts = new ThreadStart(this.doWork);
Thread oThread = new Thread(ts);
ts.Start();
// more unrelated stuff ...
}
public void doWork()
{
string error = string.Empty;
int result = 0;
try
{
result = this.service.WhatsTheStatus(out error); // lengthy operation
switch (result)
{
case 1:
this.lblStatus.Text = "OK";
break;
case -1:
this.lblStatus.Text = "Error";
this.lblError.Text = error;
break;
default:
this.lblStatus.Text = "Unknown";
break;
}
}
catch
{
}
}
Unfortunately I saw lblStatus being updated in the production environment and it isn't referenced from anywhere else in the entire application (except the Designer generated stuff, of course).
That is because cross-thread access exceptions are not guaranteed to be thrown when you run code without debugger (in windows forms). Read this for example: https://msdn.microsoft.com/en-us/library/vstudio/ms171728%28v=vs.110%29.aspx:
The .NET Framework helps you detect when you are accessing your controls in a manner that is not thread safe. When you are running your application in the debugger, and a thread other than the one which created a control tries to call that control, the debugger raises an InvalidOperationException with the message, "Control control name accessed from a thread other than the thread it was created on."
This exception occurs reliably during debugging and, under some circumstances, at run time. You might see this exception when you debug applications that you wrote with the .NET Framework prior to the .NET Framework 2.0. You are strongly advised to fix this problem when you see it, but you can disable it by setting the CheckForIllegalCrossThreadCalls property to false. This causes your control to run like it would run under Visual Studio .NET 2003 and the .NET Framework 1.1.
You can check this yourself by writing simple winforms application, set form title from another thread and see exception is thrown. Then run same application without debugger attach and see how form title will happily change without any problems.
This is specifically a Caliburn.Micro question I think, as it has to do with how CB handles navigation in windows phone 7.
I have a view that has the option of launching a phone number chooser. Once the result comes back I store it and navigate away, only the navigation wont work. I assume this is because the Handle method is working with the task and not my view. I know I can stick a button down the end of the page to navigate after the handle is finished but I would like this to happen once the result comes back.
This is what I am doing.
public void Handle(TaskCompleted<PhoneNumberResult> message)
{
webtext.Recipient = message.Result.PhoneNumber;
webtext.RecipientDisplayName = message.Result.DisplayName;
CommitWebtextToStorage();
events.Unsubscribe(this);
navigationService.UriFor<ComposeViewModel>();
}
Which wont work. I also can't call a method inside that as that would be the same as what I am doing. I need to let the handle method exit and then call the navigation service.
Actually, the navigation should look like:
navigationService.UriFor<ComposeViewModel>().Navigate();
(note the final Navigate method)
If it was just a typo in the question, I guess the issue could have to do with the timing of application resuming (which occurs when you return back to the application after the chooser task is completed).
In that case, could you please create an issue for this?
Im trying to call some windows forms code (like setting label.visible = true in some event code, everything compiles ok, but form does not react to change! What could be the problem?
Problem is in lines:
labelNewCall.Visible = true;
timerNewCall.Enabled = true;
code : http://pastebin.com/gV28PN4P
also other code did not work, until i reordered some of it (order is not important but it did not work otherwise... )
You can also try a handy little method that you can place in your inner-loop:
Application.DoEvents();
Here's the MSDN write up:
http://msdn.microsoft.com/en-us/library/system.windows.forms.application.doevents.aspx
Do you call this method in another than UI thread? If so, you should use Invoke and/or BeginInvoke method.
Look at article What's up with BeginInvoke?.
This could be because the soundCapture_BufferThrown callback function is not run on the GUI thread. Read this post for more details about threading in WinForms.
Use invoke to access object in a windows forms/controls thread
Reference - http://www.dailycoding.com/...formscontrols_thread.aspx