After some digging into exception handling in silverlight and reading some useful blogs like this
Silverlight exception handling using WCF RIA Services and WCF Services I ended up implementing similar idea in the App.xaml.cs to show an error page and call another wcf service method to log the error to the event viewer:
private void Application_UnhandledException(object sender, ApplicationUnhandledExceptionEventArgs e)
{
if (!System.Diagnostics.Debugger.IsAttached)
{
var errorPage = new Error();
errorPage.Show();
string errorMsg = string.Format("{0} {1}", e.ExceptionObject.Message, e.ExceptionObject.StackTrace);
EventHandler<WriteIntoEventLogCompletedEventArgs> callback = (s, ev) =>
{
bool result = ev.Result;
};
(new ServiceProxy<ApplicationServiceClient>()).CallService<WriteIntoEventLogCompletedEventArgs>(callback, errorMsg);
e.Handled = true;
}
}
and this is what I have in Error.xaml.cs:
private void OKButton_Click(object sender, RoutedEventArgs e)
{
this.DialogResult = true;
}
that basically will close the error page when user clicks on OK.
Everything works fine most of the cases.The problem happens when one of the callbacks to the wcf service cause an exception.The error page will be shown nicely and when user clicks ok, error page will get closed. But the background is still showing the busy indicator and the original service callback is still waiting for the response.I need to somehow terminate it.
I would be appriciative if anybody could help.
Thanks,
Sil
--
Thanks a lot for your helpful reply.I used the same idea and in the original service callback method added a code to check e.Error and if it is not null,close the window(it is a child window) with the busyindicator and everything works perfect now. Thanks again. Sil
My guess is that the original service callback may be completing but in an error condition. You may need to detect the error condition and set the IsBusy property of the busyindicator back to False.
Couple of things to check
Is the original service callback atleast returning successfully? You can check this by placing a breakpoint into the original service callback method.
Have you correctly handled the error condition in your callback method. For example -
void proxy_GetUserCompleted(object sender, GetUserCompletedEventArgs e)
{
if (e.Error != null)
{
getUserResult.Text = "Error getting the user.";
}
else
{
getUserResult.Text = "User name: " + e.Result.Name + ", age: " + e.Result.Age + ", is member: " + e.Result.IsMember;
}
}
Reference - http://msdn.microsoft.com/en-us/library/cc197937(v=VS.95).aspx
Related
I am trying to create a software in WPF which hosts a browser (WebView2 currently 1.0.818.41) and also show a OnScreenKeyboard when there is a input field focused in the browser.
I have done this kind of stuff with CefSharp in WPF before but I cannot do it with WebView2 currently. My problem is I do not find a way to send keystrokes from the OnScreenKeyboard (or from the WPF Window) to the Browser.
In CefSharp there we have a function called ChromiumWebBrowser.GetHost().SendKeyEvent() but I cannot find something similar in WebView2.
Am I blind or is this something which is currently not implemented (or maybe not planed)?
Thank you in advance!
There is no direct way. What can be done is execute some JS, which in turn posts a message to WebView. This message can then be caught back in wv2_WebMessageReceived event.
There is extensive documentation on the interop between.NET and JS and interop between JS and .NET WPF Forms here.
A solution would be to inject a sendMessage JS function in the NavigationStarting event:
private void wv2_NavigationStarting(Microsoft.UI.Xaml.Controls.WebView2 sender, Microsoft.Web.WebView2.Core.CoreWebView2NavigationStartingEventArgs args){
var sc = "function sendMessage(txt) { window.chrome.webview.postMessage(txt); }";
wv2.CoreWebView2.AddScriptToExecuteOnDocumentCreatedAsync(sc);
}
Now you collect input fields and add onfocus and onblur events to these input fields for example in the NavigationCompleted event like this:
private void wv2_NavigationCompleted(Microsoft.UI.Xaml.Controls.WebView2 sender, Microsoft.Web.WebView2.Core.CoreWebView2NavigationCompletedEventArgs args){
string script = "const collection ="+
"document.getElementsByTagName(\"input\");" +
"for (let i = 0; i < collection.length; i++){" +
"collection[i].onfocus= ()=>{ sendMessage('onFocus('+collection[i].name')'); }; " +
"collection[i].onblur= (ev)=>{ sendMessage('onBlur('+collection[i].name')'); };"+
"}";
sender.ExecuteScriptAsync(script);
}
Now catch the message in the wv2_WebMessageReceived event:
private void wv2_WebMessageReceived(Microsoft.UI.Xaml.Controls.WebView2 sender, Microsoft.Web.WebView2.Core.CoreWebView2WebMessageReceivedEventArgs args)
{
var postMess = args.TryGetWebMessageAsString();
if (postMess == "onFocus(nameOfField)" )
{
// here activate the button(keyboard)
// store the Name on focusField variable
}
if (postMess == "onBlur" && paneShown)
{
// here deactivate the button(keyboard)
// release the focusField
}
}
Now you can send a click event to the input fields:
private void btn_Clicked(Object sender, EventArgs args)
{
var script = "var field "+
"= document.getElementsByName("+focusField+");" +
" field.value+=field.value"+args.keyValue();
wv2.CoreWebView2.ExecuteScriptAsync(script);
}
wv2 is an instance of WebView2 and the code is typed directly here and not compiled. Hope you get the idea.
I use wcf service client to submit changes of data for a silverlight project. The correlative codes like this:
public class DispatcherCollection : UpdatableCollection<DocumentDispatcher>
{
public override void SubmitChanges()
{
DocumentServiceClient client = new DocumentServiceClient();
client.NewDocumentCompleted += (s, e) =>
{
// (s as DocumentServiceClient).CloseAsync();
// do something
};
client.UpdateColumnCompleted += (s, e) =>
{
// (s as DocumentServiceClient).CloseAsync();
// do something
};
client.RemoveDocumentCompleted += (s, e) =>
{
// (s as DocumentServiceClient).CloseAsync();
// do something
};
foreach (DocumentDispatcher d in this)
{
if (d.IsNew)
{
// d=>object[] data
client.NewDocumentAsync(data);
d.IsNew=false;
}
else
{
foreach (string propertyName in d.modifiedProperties)
{
client.UpdateColumnAsync(d.ID, GetPropertyValue(propertyName));
}
dd.ClearModifications();
}
}
foreach (DocumentDispatcher dd in removedItems)
{
client.RemoveDocumentAsync(dd.ID);
}
removedItems.Clear();
}
}
Class UpdatableCollection derives from ObserableCollection, and I implemtent logics in class DocumentDispatcher and UpdatableCollection to buffer the changes of data such as new created, property modified and removed. I use SubmitChanges method to submit all changes to server.
Now I am stuck:
1. I am at a loss when to close the client after a bunlde fo async calls. I don't know which callback is the last one.
2. What will happen when a user closes the IE immediately right after clicking the save button (it seems to be done because it runs async but in fact the updating threads are industriously running.)?
You can keep a counter or use an isbusy function to monitor the callbacks from your Async calls - to make sure they all finished.
If the user fires off a request to the WCF service, the WCF service will complete but there will be no call back - as the application will be closed.
I think that there is no wait handle for silverlight asynchornized call brings inconvenience. Here is my experence. I want to check and submit modifications of data which are not expicitly submitted when browser is closing. I have implemented codes in App_Exit like this:
private void Application_Exit(object sender, EventArgs e)
{
Document doc = EDPViewModel.CurrentViewModel.Document;
if (doc != null) new ServiceClient().SubmitChangesAsync(doc);
}
provided that in the SubmitChangesAsync method, not submitted modifications of doc are found out and submitted. Therefore, because of the asynchronized running features, while the service invoking is being sent, the application is yet immediately closed. And that will dispose related resouces of the application, including Service Invoking Tasks. So the codes above work not. I hope so eagerly that somewhere exists a mechanism, which can export a wait handle from silverlight asynchronized call, so that I can update the above codes whith this:
private void Application_Exit(object sender, EventArgs e)
{
Document doc = EDPViewModel.CurrentViewModel.Document;
if (doc != null)
{
Task t = new TaskFactory().StartNew(() => new ServiceClient().SubmitChangesAsync(doc));
t.Wait();
}
}
With wait operation I can really be sure that all modifications are really definitely submitted. So is there any similar pattern that can be used in silverlight?
It's for me a good news, as you put it, that calls could work like the mode "requesting and forgetting". So I needn' to worry too much about data losing during submitting.
To ensure all service calls are sent out before application is closed, I think, counter is a simple and effient idea. I will try to implement it in my project.
Thank you for your help!
I'm building a WPF application using the SimpleMVVM framework and I'm having trouble catching exceptions. I use the MessageBus of SimpleMVVM to send a message to another viewmodel. This all works fine, but I noticed that exceptions raised in the code executed by the messagebus get suppressed. Here's what I've got so far:
My MainWindow contains a button that fires a TempCommand on the MainWindowViewModel. This command in turn calls the Test method (shown below), which sends out a notification message using the MessageBus of SimpleMVVM.
private void Temp()
{
SendMessage("Temp", new NotificationEventArgs());
}
My MainWindow also contains a Frame with content. The ViewModel of this content, CustomerViewModel, has registered to receive these notifications in its constructor:
public CustomerDetailsViewModel(ICustomerServiceAgent agent)
{
RegisterToReceiveMessages("Temp", Temp);
}
Where the Temp method simply throws an exception:
private void Temp(object sender, NotificationEventArgs args)
{
throw new NotImplementedException("Somewhere, something horrible happened");
}
When I debug the application, I clearly see the Temp method being called and the exception being raised. But for some reason, that's all. The application is unaffected and my exception trapping code is unaware of the exception.
I trap exceptions in two ways. The first is by handling the event on the Dispatcher:
<Application x:Class="MyApp"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
StartupUri="MainWindow.xaml"
DispatcherUnhandledException="App_DispatcherUnhandledException">
Where the code-behind looks like:
private void App_DispatcherUnhandledException(object sender, DispatcherUnhandledExceptionEventArgs e)
{
Log("Exception: " + e.Exception.Message);
e.Handled = true;
}
public static void Log(string message)
{
File.AppendAllText(#"D:\Temp\log.txt", "[" + DateTime.Now.ToString("F") + "] [" + System.Threading.Thread.CurrentThread.ManagedThreadId.ToString() + "] " + message + Environment.NewLine);
}
This code catches some exceptions, but not all. I found out that WPF suppresses databinding exceptions by default. Because my ViewModels are bounded through the DataContext property on my view, I thought this was the problem. I found this article, which defines a TraceListener that uses the PresentationTraceSources class. Databinding exceptions now get caught, but... Not the exceptions thrown in the code executed through the MessageBus.
I've created a solution demonstrating this behavior, it can be downloaded here.
And this is where I'm stuck. What am I missing? How do I catch these exceptions?
Big thanks in advance.
JP
I think it is a bug or problem with the implementation of the MessageBus in SimpleMVVM.
Cause multiple subscribers can subscribe to a token, the current implementation ensures that each subscribed method gets called even when one registered method throws an exception. In this case the exception is catched and written out to the Console.
The method that is responsible to call a subscribed method is SafeNotify
private void SafeNotify(Action method, bool post) {
try {
// Fire the event on the UI thread
if (post){
if (Dispatcher.CheckAccess()){
method();
}
else{
Dispatcher.BeginInvoke(method);
}
}
// Fire event on a ThreadPool thread
else{
ThreadPool.QueueUserWorkItem(o => method(), null);
}
}
catch (Exception ex){
// If there's an exception write it to the Output window
Debug.WriteLine(ex.ToString());
}
}
When the method call gets queued in the ThreadPool, you have no chance to handle the thrown exception. See also this post for further information.
The only option you have is to ensure that the code of your own registered methods is always surrounded by a try-catch-block.
I'm loading user images using Silverlight 3.
Everything works fine and I can set the file stream to a BitmapImage and it gets rendered OK.
The problem is that if I try to load something that's not an image (like a .exe that's been renamed to .png) Silverlight crashes with a System.Exception that says "Catastrophic failure".
The MSDN documentation unhelpfully says that it should be so there msdn link and I should listen to the ImageFailed event (which never gets fired).
Am I missing something there or is the library broken when loading from a stream?
The code I've got loading the image from the source:
var openFileDialog = new OpenFileDialog();
openFileDialog.Filter = "*.jpg;*.jpeg;*.png|*.jpg;*.jpeg;*.png";
openFileDialog.Multiselect = false;
var showDialog = openFileDialog.ShowDialog();
if (showDialog.HasValue && showDialog.Value)
{
using (var reader = openFileDialog.File.OpenRead())
{
var picture = new BitmapImage();
picture.DownloadProgress += (o, e) => System.Threading.SynchronizationContext.Current.Send((oo) => System.Windows.Browser.HtmlPage.Window.Alert("Download progress: " + e.Progress), null);
picture.ImageFailed += (o, e) => System.Threading.SynchronizationContext.Current.Send((oo) => System.Windows.Browser.HtmlPage.Window.Alert("Image failed: " + e.ErrorException), null);
picture.ImageOpened += (o, e) => System.Threading.SynchronizationContext.Current.Send((oo) => System.Windows.Browser.HtmlPage.Window.Alert("Image opened: " + e.OriginalSource), null);
picture.SetSource(reader); // BANG! here without any of the alerts showing up
}
}
That's weird, but you're right, it does behave that way, even on Silverlight 4.
There may be a better option, but one way I've found to work around these exceptions that can't otherwise be handled is to modify the App.Application_UnhandledException() method. This would work for you:
private void Application_UnhandledException(object sender, ApplicationUnhandledExceptionEventArgs e)
{
// Handle stupid image load exception. Can't think of a better way to do it -- sorry.
if (e.ExceptionObject is System.Exception && e.ExceptionObject.Message.Contains("HRESULT") && e.ExceptionObject.Message.Contains("E_UNEXPECTED"))
{
Deployment.Current.Dispatcher.BeginInvoke(() =>
{
MessageBox.Show("Error loading image.");
});
e.Handled = true;
return;
}
// If the app is running outside of the debugger then report the exception using
// the browser's exception mechanism. On IE this will display it a yellow alert
// icon in the status bar and Firefox will display a script error.
if (!System.Diagnostics.Debugger.IsAttached)
{
// NOTE: This will allow the application to continue running after an exception has been thrown
// but not handled.
// For production applications this error handling should be replaced with something that will
// report the error to the website and stop the application.
e.Handled = true;
Deployment.Current.Dispatcher.BeginInvoke(delegate { ReportErrorToDOM(e); });
}
}
It's a hack and I don't like it, but it's better than an unhandled exception.
BTW, you really ought to file a Connect bug on this behavior. It quite certainly fails the "Law of Least Astonishment". See Tim Heuer's post on how to get the bug filed: http://timheuer.com/blog/archive/2010/05/03/ways-to-give-feedback-on-silverlight.aspx
I have a few users that are using a silverlight app that aren't recieving updates when a new release is published. Isn't this suppose to be automatic or perhaps I'm missing an option somewhere? I was also starting to think that maybe the XAP file is cached and I some how need to prevent that.
Any thoughts out there?
You need to write a few lines of code.
If you're familiar with 'one click' deployment then some of the options you're used to don't exist in Silverlight. You need to write the code yourself.
http://nerddawg.blogspot.com/2009/07/silverlight-out-of-browser-apps-how.html
private void Application_Startup(object sender, StartupEventArgs e)
{
this.RootVisual = new MainPage();
if (Application.Current.IsRunningOutOfBrowser)
{
Application.Current.CheckAndDownloadUpdateAsync();
}
and then in your App() constructor :
Application.Current.CheckAndDownloadUpdateCompleted +=
new CheckAndDownloadUpdateCompletedEventHandler(Current_CheckAndDownloadUpdateCompleted);
and an event handler :
void Current_CheckAndDownloadUpdateCompleted(object sender, CheckAndDownloadUpdateCompletedEventArgs e)
{
// http://nerddawg.blogspot.com/2009/07/silverlight-out-of-browser-apps-how.html
if (e.UpdateAvailable)
{
MessageBox.Show("The application has been updated! Please close and reopen it to load the new version.");
}
else if (e.Error != null && e.Error is PlatformNotSupportedException)
{
MessageBox.Show("An application update is available, " +
"but it requires a new version of Silverlight. " +
"Please contact tech support for further instructions.");
}
}
It only auto updates if the developer performs the CheckAndDownloadUpdateAsync() call. See updates: http://timheuer.com/blog/archive/2009/07/10/silverlight-3-released-what-is-new-and-changed.aspx#oob