Windows Form TopMost don't work with BackgroundWorker? - backgroundworker

I'm trying to show window when user need to be notify about some work to do. Every think work fine, but i want to show form absolute topmost. I set form property TopMost = true but it does not work, window still show behind other forms.
I figure out that TopMost = true don't work only with BackgroundWorker, when i use Timer class it work fine. I'm wonder why? Anybody can explain me this?
Here is simple example what i want to do.
static void Main(string[] args)
{
try
{
BackgroundWorker worker = new BackgroundWorker();
worker.DoWork += new DoWorkEventHandler(worker_DoWork);
worker.RunWorkerAsync();
Application.Run(new Form());
}
catch (Exception exp)
{
Console.WriteLine(exp);
}
}
static void worker_DoWork(object sender, DoWorkEventArgs e)
{
while (true)
{
System.Threading.Thread.Sleep(1000);
if (NeedNotify())
{
NotifyForm myNotifyForm = new NotifyForm();
myNotifyForm.TopMost = true;
myNotifyForm.ShowDialog(); // NotifyForm still show behind others windows
}
}
}
private static bool NeedNotify()
{
return true;
}
}

Creating the form within the background worker causes the form to be created on a different thread. Instead, create and show the form in your main thread before calling RunWorkerAsync.
Another problem may arise from the fact that you're creating the "notification" before the application's main loop is even started. You may consider reorganizing your code so that the background worker is started from the main form's OnLoad event.

Related

Why ActivityIndicator changes state after entire method is completed?

I would like to show ActivityIndicator object after user tap the login button on page. Unfortunately there is small problem to do that because it seems like ActivityIndicator change state after entire method is completed. This is code I wrote so far:
private void Login(object sender, EventArgs ev)
{
BusyIndicator.IsVisible = true; //<- here I want to show indicator
try
{
//some input validation, connection opening etc
ConnectionHandler.OpenConnection(ServerIP, "dmg", false);
}
catch (Exception e)
{
Logging.Error(e.Message, "Connection", e);
}
}
When I set breakpoint after BusyIndicator.IsVisible = true; there is absolutely no change in app. However I noticed that when method is completed then indicator is shown. Is this a correct behavior of this control?
Why I need this? Because field validation and connecting with server takes some time and I need to show to user that something happens in background. Login function takes ~1 sec so indicator show and hide quickly I can't even see any change.
How can I show indicator immediately after user tap a button?
Your problem is that Login() method is being executed in the UI thread. So, despite setting BusyIndicator.IsVisible = true;, the thread continues tio execute the method to get data, so the UI does not respond.
Solution, run the OpenConnection in a different thread:
private async void Login(object sender, EventArgs ev)
{
BusyIndicator.IsVisible = true; //<- here I want to show indicator
try
{
//some input validation, connection opening etc
await Task.Run(() => { ConnectionHandler.OpenConnection(ServerIP, "dmg", false);});
}
catch (Exception e)
{
Logging.Error(e.Message, "Connection", e);
}
}

Launching from UWP URI Protocol Scheme is Not Navigating

I have followed the instructions as found in the documentation; however, when I launch my app using the specified protocol my-protocol:// (typed into a web browser), the app will launch but then it just stays on the splash screen, as if the navigation fails to do anything:
Code Example:
// MyApp.UWP/App.xaml.cs
protected override void OnActivated(IActivatedEventArgs args)
{
if (args.Kind == ActivationKind.Protocol)
{
ProtocolActivatedEventArgs eventArgs =
args as ProtocolActivatedEventArgs;
// TODO: Decide where to navigate, but for now just go to main page
Frame rootFrame = Window.Current.Content as Frame;
rootFrame.Navigate(typeof(MainPage), args);
}
}
Is there something obvious that I am doing wrong? Perhaps there is a better way to handle navigation? Or perhaps there is something that I overlooked?
Edit
This is particularly hard to troubleshoot, since I can't just run with debug in visual studio. To test it out I actually have to launch it from the my-protocol://, which is not connected to the debugger.
Is there a way to debug this when launched from the url / protocol?
I could reproduce your issue. #kennyzx's suggestion was correct. You would first need to do judgement before navigating.
Please refer to the following code sample for reference.
protected override void OnActivated(IActivatedEventArgs args)
{
base.OnActivated(args);
if (args.Kind == ActivationKind.Protocol)
{
ProtocolActivatedEventArgs eventArgs =
args as ProtocolActivatedEventArgs;
// TODO: Decide where to navigate, but for now just go to main page
Frame rootFrame = Window.Current.Content as Frame;
if (rootFrame == null)
{
rootFrame = new Frame();
}
Window.Current.Content = rootFrame;
rootFrame.Navigate(typeof(MainPage), args);
Window.Current.Activate();
}
}

CaliburnMicro StackOverflowException when ActivateItem function is invoked

I have two VM - View (inherited from Screen) and Edit (inherited from Screen). View is used to display grid with data and Edit - add/edit new items into grid.
In my ShellViewModel I have the following code to activate View.
public void WorkstationView()
{
this.ActivateItem(ServiceLocator.Current.GetInstance<WorkstationViewModel>());
}
In WorkstationViewModel when user clicks on the Create button the following code is invoked
public void CreateAction()
{
EditableObject = new WorkstationDto();
TryClose(true);
}
And there is a listener to Deactivated event property, see code below (InitViewModels is invoked in ShellViewModel constructor).
private void InitViewModels()
{
#region Init
WorkstationViewModel = ServiceLocator.Current.GetInstance<WorkstationViewModel>();
WorkstationEditViewModel = ServiceLocator.Current.GetInstance<WorkstationEditViewModel>();
#endregion
#region Logic
WorkstationViewModel.Deactivated += (o, args) =>
{
if (WorkstationViewModel.EditableObject == null)
{
return;
}
WorkstationEditViewModel.EditableObject = WorkstationViewModel.EditableObject;
ActivateItem(WorkstationEditViewModel);
};
#endregion
}
The problem here is a StackOverflow exception when I close Edit view (see create action).
“Since the Conductor does not maintain a “screen collection,” the activation of each new item causes both the deactivation and close of the previously active item.” Caliburn.Micro documentation
If you are using Conductor<T>, then ActivateItem(WorkstationEditViewModel); inside of the Deactivated handler is implicitly re-triggering the deactivation of the previous viewmodel - giving you an infinite loop. Try changing your conductor to inherit from Conductor<IScreen>.Collection.OneActive instead. However, you will still have two deactivations: the one from the original TryClose operation, and a second one when you activate the new screen. Overriding DetermineNextItemToActivate can help you avoid that.

Detect browser refresh

How can I find out if the user pressed F5 to refresh my page (Something like how SO implemented. If you refresh your page, the question counter is not increased). I have tested many code snippets mentioned in a dozen of tutorials, but none worked correctly.
To be more clear, suppose that i have an empty web form and would like to detect whether the user has pressed F5 in client-side (causing a refresh not submit) or not.
I can use session variables, but if the user navigates to another page of my site, and then comes back , I'd like to consider it as a new visit, not a refresh. so this is not a session-scope variable.
Thanks.
Update: The only workaround I could find was to inherit my pages from a base page, override the load method like below:
public class PageBase : System.Web.UI.Page
{
protected override void OnLoad(EventArgs e)
{
base.OnLoad(e);
this.Session["LastViewedPage"] = Request.RawUrl;
}
}
and in every page if I was interested to know if this is a refresh:
if (this.Session["LastViewedPage"].ToString() == Request.RawUrl)
{
// This is a refresh!
}
I run into this problem and use the following code. It works well for me.
bool isPageRefreshed = false;
protected void Page_Load(object sender, EventArgs args)
{
if (!IsPostBack)
{
ViewState["ViewStateId"] = System.Guid.NewGuid().ToString();
Session["SessionId"] = ViewState["ViewStateId"].ToString();
}
else
{
if (ViewState["ViewStateId"].ToString() != Session["SessionId"].ToString())
{
isPageRefreshed = true;
}
Session["SessionId"] = System.Guid.NewGuid().ToString();
ViewState["ViewStateId"] = Session["SessionId"].ToString();
}
}
The only sure solution is to make a redirect to the same page , and here is a similar question: Post-Redirect-Get with ASP.NET
But there are also some other tricks, by adding some ticket on the page and see if this is the same or have change, see the full example and code at:
http://www.codeproject.com/Articles/68371/Detecting-Refresh-or-Postback-in-ASP-NET
and one more:
http://dotnetslackers.com/community/blogs/simoneb/archive/2007/01/06/Using-an-HttpModule-to-detect-page-refresh.aspx

Force Method to Run During Event

Is there a way to force methods to be accessible only during certain events during the page life cycle. For example, I have a extension to System.Web.UI.Page that adds a PrependTitle method.
I also have a masterpage that embeds another masterpage. The first masterpage sets the base title (Google), the next masterpage prepends the title (Calendar), and a page also prepends the title (21 May 2011).
The result should be:
21 May 2011 :: Calendar :: Google
And this is the case when the PrependTitle is run during the Page_Init event. However, when the method is run during Page_Load the following the results:
Google
So, that brings me to the question: How can it be enforced that a method only be accessible during specified life cycle events?
// The Method Mentioned
public static class PageExtensions
{
public static void PrependTitle(this Page page, string newTitle)
{
page.Title = newTitle + " " + Global.TITLE_DELIMITER + " " + page.Title;
}
}
I think this can be done similar to the following. The general idea is declare the method as private, declare the ones that should have access to it as sealed
class AppsBasePage : Page
{
abstract void PrependTitle(string title);
}
class PageWithTitlePrepended : AppsBasePage
{
private void PrependTitle(string title)
{
Title = String.Format("{0} {1} {2}", newTitle, Global.TITLE_DELIMITER, Title);
}
protected sealed override void Page_Init(object sender, EventArgs e)
{
PrependTitle("This is a title")
}
}
class ActualPageInApp: PageWithTitlePrepended
{
override void Page_Load(object s, EventArgs e)
{
// can't access PrependTitle here
}
}
This solves your question in bold, but I'm not convinced this situation is what is causing your problem with PrependTitle specifically. I think more code / context would be needed to solve your actual problem
If you want to brute force ensure that the method is being called from Init, you can inspect the call stack. Something like this:
public static bool CalledFromInit()
{
//Grab the current Stack Trace and loop through each frame
foreach(var callFrame in new StackTrace().GetFrames())
{
//Get the method in which the frame is executing
var method = callFrame.GetMethod();
//Check if the method is Control.OnInit (or any other method you want to test for)
if(method.DeclaringType == typeof(Control) && method.Name == "OnInit")
//If so, return right away
return true;
}
//Otherwise, we didn't find the method in the callstack
return false;
}
Then you would use it like:
public static void PrependTitle(this Page page, string newTitle)
{
//If we aren't called from Init, do something
if (!CalledFromInit())
{
//We could either return to silently ignore the problem
return;
//Or we could throw an exception to let the developer know they
// did something wrong
throw new ApplicationException("Invalid call to PrependTitle");
}
//Do the normally processing
page.Title = newTitle + " " + Global.TITLE_DELIMITER + " " + page.Title;
}
However, I'd caution that the stack trace isn't the most reliable thing. In release, code could get optimized such that the Control.OnInit method is inlined so your code wouldn't be able to see it in the call stack. You could wrap this check in an #if DEBUG block so it only executes during development. Depending on your use case, it might be good enough to catch this problem while in DEBUG and not bother doing the check in RELEASE. But that's up to you.
Another option...building on Tommy Hinrichs answer, if all your pages inherit from a base class, you'll be able to do it a bit more reliably. I'd suggest something like this:
public abstract class BasePage : Page
{
private bool _executingInit;
protected internal override void OnPreInit(EventArgs e)
{
_executingInit = true;
base.OnPreInit(e);
}
protected internal override void OnInitComplete(EventArgs e)
{
base.OnInitComplete(e);
_executingInit = true;
}
public void PrependTitle(string newTitle)
{
if (!_executingInit)
throw new ApplicationException("Invalid call to PrependTitle.");
Title = newTitle + " " + Global.TITLE_DELIMITER + " " + Title;
}
}
That way, PrependTitle will throw an exception unless it's called between PreInit and InitComplete (which sounds like exactly what you want).
As one last option, you could be sneaky and use reflection to access the Control.ControlState property (which is a confusing name because it's not related to Control State - the thing similar to View State). That property tracks the Control as it goes throw its lifecycle - and it has the following values:
internal enum ControlState
{
Constructed,
FrameworkInitialized,
ChildrenInitialized,
Initialized,
ViewStateLoaded,
Loaded,
PreRendered
}
You'll notice that Enum is internal. So is the Control.ControlState property. But with Reflection, you could use that - and you could even use it from an extension method that is external to the Page.
Hope one of those ways will work for you!
Your best bet is probably to use the Handles Keyword to attach the method to the event.
You might have to create a subclass of System.Web.UI.Page to ensure this is enforced.
It seems that the issue is in the prependTitle method, it should append the text to the page title not replace it.
Just call the PrependTitle method in the page_load of each mashterpage and page and append the text to the title.

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