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Trying to play multiple videos in wpf but it only took the last video

I don't know if i am doing it correctly.
Here I'm trying to play all the videos from the video folder in wpf C# but it only plays the last video , how can i fix this
// Go to video folder.
var videosFolder = KnownFolders.VideosLibrary;
// Here i get all the files in the video folder.
var files = await videosFolder.GetFilesAsync();
// If there is no file do nothing.
if (files.Count == 0)
{
return;
}
// Here i am looping all the videos.
foreach (var video in files)
{
// Accessing each file in the video folder.
var file = await StorageFile.GetFileFromPathAsync(video.Path);
// ...
if (file == null)
{
return;
}
// Getting the path of a file.
var source = MediaSource.CreateFromStorageFile(file);
// ...
VideoPlayer.SetPlaybackSource(source);
}

You are not waiting for each video to complete before starting to play the next one. This is why you only see the last one actually play.

You have to subscribe to MediaEnded event from MediaElement documentations:
Occurs when the MediaElement finishes playing audio or video.
Here is a sample code (not tested!):
// subscribe once
VideoPlayer.MediaEnded += OnMediaEnded;
private void OnMediaEnded(object sender, RoutedEventArgs e)
{
var nextMediaSource = GetNextMediaSource();
if(nextMediaSource != null)
VideoPlayer.SetPlaybackSource(nextMediaSource);
}

Windows Phone, pick file using PickSingleFileAndContinue or PickMultipleFilesAndContinue

I got stuck trying to implementing file picker for windows phone app. I need to choose files from gallery using FileOpenPicker. I didn't get how it works. Here is my code:
private readonly FileOpenPicker photoPicker = new FileOpenPicker();
// This is a constructor
public MainPage()
{
// < ... >
photoPicker.SuggestedStartLocation = PickerLocationId.PicturesLibrary;
photoPicker.FileTypeFilter.Add(".jpg");
}
// I have button on the UI. On click, app shows picker where I can choose a file
private void bChoosePhoto_OnClick(object sender, RoutedEventArgs e)
{
photoPicker.PickMultipleFilesAndContinue();
}
So, what to do next? I guess I need to get a file object or something.
I found this link. It is msdn explanation where custom class ContinuationManager is implemented. This solution looks weird and ugly. I am not sure if it is the best one. Please help!

PickAndContinue is the only method that would work on Windows Phone 8.1. It's not so weird and ugly, here goes a simple example without ContinuationManager:
Let's assume that you want to pick a .jpg file, you use FileOpenPicker:
FileOpenPicker picker = new FileOpenPicker();
picker.FileTypeFilter.Add(".jpg");
picker.ContinuationData.Add("keyParameter", "Parameter"); // some data which you can pass
picker.PickSingleFileAndContinue();
Once you run PickSingleFileAndContinue();, your app is deactivated. When you finish picking a file, then OnActivated event is fired, where you can read the file(s) you have picked:
protected async override void OnActivated(IActivatedEventArgs args)
{
var continuationEventArgs = args as IContinuationActivatedEventArgs;
if (continuationEventArgs != null)
{
switch (continuationEventArgs.Kind)
{
case ActivationKind.PickFileContinuation:
FileOpenPickerContinuationEventArgs arguments = continuationEventArgs as FileOpenPickerContinuationEventArgs;
string passedData = (string)arguments.ContinuationData["keyParameter"];
StorageFile file = arguments.Files.FirstOrDefault(); // your picked file
// do what you want
break;
// rest of the code - other continuation, window activation etc.
Note that when you run file picker, your app is deactivated and in some rare situations it can be terminated by OS (little resources for example).
The ContinuationManager is only a helper that should help to make some things easier. Of course, you can implement your own behaviour for simpler cases.

Windows Phone 8 can´t call AudioVideoCaptureDevice second time

In my App you can open a Site where you can switch on and off the Flashlight.
The first time it works, but if I try to switch the flashlight on a second time the App crashes.
I think this is a Problem with AudioVideoCaptureDevice.OpenAsync. If I call it a second time the App crashes with a System.Reflection.TargetInvocationException WinRT-Informationen: Unable to acquire the camera. You can only use this class while in the foreground.
Someone know this Problem?
protected AudioVideoCaptureDevice Device { get; set; }
public Page10()
{
InitializeComponent();
}
async void tglSwitch_Checked(object sender, RoutedEventArgs e)
{
var sensorLocation = CameraSensorLocation.Back;
if (this.Device == null)
{
// get the AudioVideoCaptureDevice
this.Device = await AudioVideoCaptureDevice.OpenAsync(sensorLocation,
AudioVideoCaptureDevice.GetAvailableCaptureResolutions(sensorLocation).First());
}
var supportedCameraModes = AudioVideoCaptureDevice
.GetSupportedPropertyValues(sensorLocation, KnownCameraAudioVideoProperties.VideoTorchMode);
if (supportedCameraModes.ToList().Contains((UInt32)VideoTorchMode.On))
{
this.Device.SetProperty(KnownCameraAudioVideoProperties.VideoTorchMode, VideoTorchMode.On);
// set flash power to maxinum
this.Device.SetProperty(KnownCameraAudioVideoProperties.VideoTorchPower,
AudioVideoCaptureDevice.GetSupportedPropertyRange(sensorLocation, KnownCameraAudioVideoProperties.VideoTorchPower).Max);
this.tglSwitch.Content = "Light on";
this.tglSwitch.SwitchForeground = new SolidColorBrush(Colors.Green);
}
}
void tglSwitch_Unchecked(object sender, RoutedEventArgs e)
{
var sensorLocation = CameraSensorLocation.Back;
sensorLocation = CameraSensorLocation.Back;
var supportedCameraModes = AudioVideoCaptureDevice
.GetSupportedPropertyValues(sensorLocation, KnownCameraAudioVideoProperties.VideoTorchMode);
if (this.Device != null && supportedCameraModes.ToList().Contains((UInt32)VideoTorchMode.Off))
{
this.Device.SetProperty(KnownCameraAudioVideoProperties.VideoTorchMode, VideoTorchMode.Off);
this.tglSwitch.Content = "Light off";
}
}

I would recommend to initialize the camera with OpenAsync ONE TIME in page lifecycle, for example in OnNavigatedTo event. And only makeSetProperty() methods calls code in your checkbox events to control light. It is also very important to dispose camera correctly then leaving the page, for example in OnNavigatedFrom event, by calling device.Dispose(). This option also make your flashlight to work faster.
Keep in mind that Windows Phone 8.1 now has dedicated API for torch, which works great and the code is more beautiful. You can use in Silverlight project as well, but you have to migrate your project. Here is more about this http://developer.nokia.com/community/wiki/Using_the_camera_light_in_Windows_Phone_7,_8_and_8.1 and https://msdn.microsoft.com/en-us/library/windows/apps/windows.media.devices.torchcontrol.

MediaElement Source cannot be set after SaveState/LoadState

(Note: All code has been severely simplified.)
Problem
MediaElement source not being set after Suspend/Resume. The CurrentState quickly changes to "Closed" after the source is set.
I am handling the MediaFailed event — it doesn't fire. I am also handling the MediaOpened event, which doesn't fire either.
Details
I have the following method which updates the MediaElement's Source. It works really well as long as the app is not trying to resume after having been Suspended.
private async void UpdateMediaElementSource(object sender, EventArgs e)
{
var videoSource = this.DefaultViewModel.CurrentSource; // a string
var file = await StorageFile.GetFileFromPathAsync(videoSource);
var videoStream = await file.OpenAsync(FileAccessMode.Read);
this.videoMediaElement.SetSource(videoStream, file.ContentType);
// The above line works many times as long as the app is not trying to Resume.
}
When the app is Suspended it calls the SaveState method:
protected async override void SaveState(Dictionary<String, Object> pageState)
{
pageState["MediaElementSource"] = this.DefaultViewModel.CurrentSource;
// I also made the videoStream global so I can dispose it — but no dice.
this.videoStream.Dispose();
this.videoStream = null;
}
When the app Resumes, it calls the LoadState method:
protected async override void LoadState(Object navigationParameter, Dictionary<String, Object> pageState)
{
string source = string.Empty;
if (pageState != null)
{
if (pageState.ContainsKey("MediaElementSource"))
{
source = (string)pageState["MediaElementSource"];
}
}
var document = PublicationService.GetDocument(this.currentDocumentIdNumber);
this.DefaultViewModel = new DocumentViewModel(document);
this.DefaultViewModel.CurrentMarkerSourceChanged += UpdateMediaElementSource;
if (!string.IsNullOrEmpty(source))
{
// This causes the UpdateMediaElementSource() method to run.
this.DefaultViewModel.CurrentSource = source;
}
}
I appreciate any help on this issue. Please let me know if you need more details.

So, it turns out that the mediaElement's Source was being set before it was added to the visual tree.
Usually, this is not an issue when doing this:
mediaElement.Source = whatever;
but it IS an issue when you do this:
mediaElement.SetSource(stream, MimeType);
Conclusion
Make sure that your MediaElement is part of the VisualTree when you call SetSource(...).
A simple way to get my above code to work is by adding a global bool that is set to true once the mediaElement.Loaded event has fired. Then, inside the code that calls SetSource(), wrap that in an if(_mediaElementLoaded) block.

Odd File Association Handling Bug

I have this in App.xaml.cs:
protected override void OnFileActivated(FileActivatedEventArgs args)
{
Window.Current.Content = new Frame();
((Frame)Window.Current.Content).Navigate(typeof(MainPage), args);
Window.Current.Activate();
}
This in MainPage.xaml.cs:
protected override async void OnNavigatedTo(NavigationEventArgs e)
{
FileActivatedEventArgs filesArgs = (FileActivatedEventArgs)e.Parameter;
StorageFile file = (StorageFile)filesArgs.Files[0];
mc.SetSource(await file.OpenReadAsync(), file.ContentType);
mc.Play();
}
And this in MainPage.xaml:
<MediaElement x:Name="mc" />
Now, I am facing a very odd problem. I have associated my app with .MP4 files. Whenever, I open any file, it doesn't get played immediately. For eg.
I open a.mp4, it doesn't get played and I don't close the app.
I open b.mp4, it doesn't get played and I don't close the app.
Then, I open a.mp4, it gets played. If it doesn't, I try again and it gets played. Now if I open any MP4 file, it gets played without any problems until I close the app.
So, this workaround works sometimes:
protected override async void OnNavigatedTo(NavigationEventArgs e)
{
FileActivatedEventArgs filesArgs = (FileActivatedEventArgs)e.Parameter;
StorageFile file = (StorageFile)filesArgs.Files[0];
StorageFile file2 = (StorageFile)filesArgs.Files[0];
mc.SetSource(await file2.OpenReadAsync(), file2.ContentType);
mc.SetSource(await file2.OpenReadAsync(), file2.ContentType);
mc.Play();
}
Does anyone know why it is not working without the workaround?

It looks as if the file doesn't play if you set the source and start playing to early, before the control is intialized and/or completely loaded. That's the reason why it works on subsequent calls when the app is already loaded and occasionally even on the first call. I made a simple app and managed to reproduce your problem most of the tries (although sometimes it worked).
I tried a simple workaround to always wait for the MediaElement to get loaded before I started playing and it seems that the problem is gone - I couldn't reproduce it in more than a dozen calls.
Here's what I've done:
MainPage.xaml:
<MediaElement x:Name="mc" Loaded="mc_Loaded" />
MainPage.xaml.cs
bool loaded = false;
Task task = new Task(() => {});
private void mc_Loaded(object sender, RoutedEventArgs e)
{
loaded = true;
task.Start();
}
protected override async void OnNavigatedTo(NavigationEventArgs e)
{
FileActivatedEventArgs filesArgs = (FileActivatedEventArgs)e.Parameter;
StorageFile file = (StorageFile)filesArgs.Files[0];
if (!loaded)
await task;
mc.SetSource(await file.OpenReadAsync(), file.ContentType);
mc.Play();
}
I don't really like my solution because it's only based on guessing and empirical testing, but I couldn't find any documentation stating what needs to happen to MediaElement before it's ready.