We Keep Coding

Problems working with async Task and Textbox.Text = "Hello"

First of all, sorry because I am so new at C# and I decided to make this question because I have been choked in this for hours.
I have an GUI that works with Google Cloud Speech services and make a Speech-to-Text operation. I share with you the whole method that runs when a button is clicked:
private async Task<object> StreamingMicRecognizeAsync(int seconds)
{
if (NAudio.Wave.WaveIn.DeviceCount < 1)
{
Console.WriteLine("No microphone!");
return -1;
}
GoogleCredential googleCredential;
using (Stream m = new FileStream(#"..\..\credentials.json", FileMode.Open))
googleCredential = GoogleCredential.FromStream(m);
var channel = new Grpc.Core.Channel(SpeechClient.DefaultEndpoint.Host,
googleCredential.ToChannelCredentials());
var speech = SpeechClient.Create(channel);
var streamingCall = speech.StreamingRecognize();
// Write the initial request with the config.
await streamingCall.WriteAsync(
new StreamingRecognizeRequest()
{
StreamingConfig = new StreamingRecognitionConfig()
{
Config = new RecognitionConfig()
{
Encoding =
RecognitionConfig.Types.AudioEncoding.Linear16,
SampleRateHertz = 48000,
LanguageCode = "es-ES",
},
InterimResults = true,
}
});
// Read from the microphone and stream to API.
object writeLock = new object();
bool writeMore = true;
var waveIn = new NAudio.Wave.WaveInEvent();
waveIn.DeviceNumber = 0;
waveIn.WaveFormat = new NAudio.Wave.WaveFormat(48000, 1);
waveIn.DataAvailable +=
(object sender, NAudio.Wave.WaveInEventArgs args) =>
{
lock (writeLock)
{
if (!writeMore) return;
streamingCall.WriteAsync(
new StreamingRecognizeRequest()
{
AudioContent = Google.Protobuf.ByteString
.CopyFrom(args.Buffer, 0, args.BytesRecorded)
}).Wait();
}
};
// Print responses as they arrive.
Task printResponses = Task.Run(async () =>
{
while (await streamingCall.ResponseStream.MoveNext(default(CancellationToken)))
{
foreach (var result in streamingCall.ResponseStream
.Current.Results)
{
foreach (var alternative in result.Alternatives)
{
Console.WriteLine(alternative.Transcript);
//Textbox1.Text = alternative.Transcript;
}
}
}
});
waveIn.StartRecording();
Console.WriteLine("Speak now.");
Result_Tone.Text = "Speak now:\n\n";
await Task.Delay(TimeSpan.FromSeconds(seconds));
// Stop recording and shut down.
waveIn.StopRecording();
lock (writeLock) writeMore = false;
await streamingCall.WriteCompleteAsync();
await printResponses;
return 0;
}
My problem is that I want to update the content of the Textbox1control but it doesn´t work. It writes perfectly the output into the console with the line Console.WriteLine(alternative.Transcript); but not into my textbox.
If someone could help I would appreciate so much his help.

The problem is that you're using Task.Run, which means your code will be running on a thread-pool thread.
Instead of calling Task.Run(), just move that code into a separate async method:
async Task DisplayResponses(IAsyncEnumerator<StreamingRecognizeResponse> responses)
{
while (await responses.MoveNext(default(CancellationToken)))
{
foreach (var result in responses.Current.Results)
{
foreach (var alternative in result.Alternatives)
{
Textbox1.Text = alternative.Transcript;
}
}
}
}
Then call that method directly (without Task.Run) from code that's already on the UI thread (e.g. an event handler).
The async machinery will make sure that after the await expression, you're back on the UI thread (the same synchronization context). So the assignment to the Text property will occur on the UI thread, and all should be well.
For example:
// This would be registered as the event handler for a button
void HandleButtonClick(object sender, EventArgs e)
{
var stream = client.StreamingRecognize();
// Send the initial config request
await stream.WriteAsync(...);
// Presumably you want to send audio data...
StartSendingAudioData(stream);
await DisplayResponses(stream.ResponseStream);
}

Tasks run on seperate threads, so you must Invoke an action that will be performed on the control's thread
Textbox1.Invoke(new Action(() =>
{
Textbox1.Text= "";
}));
Edit: For WPF, I believe the equivalent is
Textbox1.Dispatcher.Invoke(new Action(() =>
{
Textbox1.Text= "";
}));

have you tried using Dispatcher.InvokeASync()?
await Dispatcher.InvokeAsync(() => {while (await streamingCall.ResponseStream.MoveNext(default(CancellationToken)))
{
foreach (var result in streamingCall.ResponseStream
.Current.Results)
{
foreach (var alternative in result.Alternatives)
{
Textbox1.Text = alternative.Transcript;
}
}
}});

How to combine asynchronous method with synchronous method in C#?

I'm calling from the main method:
public MainPage()
{
Text_to_Speech.changetospeech("Welcome to Nepal!", newmedia).Wait();
mytxtblck.Text="Hello from Nepal!"
}
What I really want to do is Wait until "Welcome to Nepal" is being spoken and then write "Hello" in mytextblck.
I've gone to several threads and worked, but nothing could make it work.
public async static Task changetospeech(string text, MediaElement mediaa)
{
var synth = new SpeechSynthesizer();
var voices = SpeechSynthesizer.AllVoices;
synth.Voice = voices.First(x => x.Gender == VoiceGender.Female );
SpeechSynthesisStream stream = await synth.SynthesizeTextToStreamAsync(text);
MediaElement media = mediaa;
media.SetSource(stream,stream.ContentType);
media.Play();
}

It sounds like what you really want is to trigger the text change when the MediaEnded event is fired.
You could do that within your ChangeToSpeech method, although it'll be a little ugly:
public async static Task ChangeToSpeech(string text, MediaElement media)
{
var synth = new SpeechSynthesizer();
var voices = SpeechSynthesizer.AllVoices;
synth.Voice = voices.First(x => x.Gender == VoiceGender.Female);
SpeechSynthesisStream stream = await synth.SynthesizeTextToStreamAsync(text);
var tcs = new TaskCompletionSource<int>();
RoutedEventHandler handler = delegate { tcs.TrySetResult(10); };
media.MediaEnded += handler;
try
{
media.SetSource(stream, stream.ContentType);
media.Play();
// Asynchronously wait for the event to fire
await tcs.Task;
}
finally
{
media.MediaEnded -= handler;
}
}

Repeat async task by timer in xamarin forms

i'm new to xamarin.forms development and i'm still having my first steps from the few tutorials that are found on the net.
I have an async task that returns the time from date.jsontest.com
and i have a timer that decrements a text in a label.
i want to put the async task in the timer so that it repeats itself and displays the time on the label however im getting cannot convert async lamba to func
here's my code please help me, thanks
static async Task<string> RequestTimeAsync()
{
using (var client = new HttpClient())
{
var jsonString = await client.GetStringAsync("http://date.jsontest.com/");
var jsonObject = JObject.Parse(jsonString);
return jsonObject["time"].Value<string>();
}
}
protected override async void OnAppearing()
{
base.OnAppearing();
timeLabel.Text = await RequestTimeAsync();
Device.StartTimer(TimeSpan.FromSeconds(1), () => { // i want the taks to be put
//here so that it gets repeated
var number = float.Parse(button.Text) - 1;
button.Text = number.ToString();
return number > 0;
});
}
Reloading the Content Page in the timer would do the trick, so if anybody can please help me it would be appreciated

You just need to wrap the async method call in a Task.Run(), for example:
Device.StartTimer(TimeSpan.FromSeconds(1), () =>
{
Task.Run(async () =>
{
var time = await RequestTimeAsync();
// do something with time...
});
return true;
});

Solved
as simple as that
private async void ContinuousWebRequest()
{
while (_keepPolling)
{
timeLabel.Text = "call: "+counter+" "+ await RequestTimeAsync()+Environment.NewLine;
// Update the UI (because of async/await magic, this is still in the UI thread!)
if (_keepPolling)
{
await Task.Delay(TimeSpan.FromSeconds(5));
}
}
}
static async Task<string> RequestTimeAsync()
{
using (var client = new HttpClient())
{
var jsonString = await client.GetStringAsync("http://date.jsontest.com/");
var jsonObject = JObject.Parse(jsonString);
TimePage.counter++;
return jsonObject["time"].Value<string>();
}
}

A simple clock demonstrates a one second timer action:
Device.StartTimer(TimeSpan.FromSeconds(1), doitt);
bool doitt()
{
label1.Text = DateTime.Now.ToString("h:mm:ss");
return true;
}

or you can try this:
static async Task<string> RequestTimeAsync()
{
using (var client = new HttpClient())
{
var jsonString = await client.GetStringAsync("http://date.jsontest.com/");
var jsonObject = JObject.Parse(jsonString);
return jsonObject["time"].Value<string>();
}
}
protected override async void OnAppearing()
{
base.OnAppearing();
var Text = await RequestTimeAsync();
Device.StartTimer(TimeSpan.FromSeconds(1), () => {
// i want the taks to be put
//here so that it gets repeated
var jsonDateTsk = RequestTimeAsync();
jsonDateTsk.Wait();
var jsonTime = jsonDateTsk.Result;
var number = float.Parse(Text) - 1;
var btnText = $"{number}";
return number > 0;
});
}

uwp async method skipping code lines

I have an async method with void return type. Here it is
public static async void LoadPlaylists()
{
if(playlistitems.Count==0)
{
var playlists = await ApplicationData.Current.LocalFolder.GetFilesAsync();
var c = playlists.Count;
foreach (var playlist in playlists)
{
var p = await Playlist.LoadAsync(playlist);
var image = new BitmapImage();
if (p.Files.Count == 0)
{
image.UriSource = new Uri("ms-appx:///Assets/Wide310x150Logo.scale-200.png");
}
else
{
image = await Thumbnail(p.Files[0]);
}
playlistitems.Add
(
new PlaylistItem
{
playlist = p,
PlaylistName = playlist.DisplayName,
NumOfVid = p.Files.Count.ToString(),
Thumbnail = image
}
);
}
}
}
It is a public static method so I can use it anywhere, I use it on one page to load some data and it works fine,and it completes this method and then move forward on next code line. as shown below
private void l1_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
//some more code
LoadPlaylists();
//some more code
}
But when I use it on another page in another event handler, which is not async method, it just runs the first line, and then it skips whole method and moves forward. I know for sure that it is skipping those lines, bcz i checked with break point, I know it is skipping because it is async but I dnt want that, I just want it to complete the whole method and then move forward. S o that I dont get any problem on next code lines. I am pasting the code below again, to show you with comments what it skipps.
public static async void LoadPlaylists()
{
if(playlistitems.Count==0)
{
//it runs till here, when compiler goes to line below
//it skips whole methods and exits it.
var playlists = await ApplicationData.Current.LocalFolder.GetFilesAsync();
var c = playlists.Count;
foreach (var playlist in playlists)
{
var p = await Playlist.LoadAsync(playlist);
var image = new BitmapImage();
if (p.Files.Count == 0)
{
image.UriSource = new Uri("ms-appx:///Assets/Wide310x150Logo.scale-200.png");
}
else
{
image = await Thumbnail(p.Files[0]);
}
playlistitems.Add
(
new PlaylistItem
{
playlist = p,
PlaylistName = playlist.DisplayName,
NumOfVid = p.Files.Count.ToString(),
Thumbnail = image
}
);
}
}
}
Now below is the code where I am using it in an async event handler, and whre it is causing me problem.
private async void ME_MediaOpened(object sender, RoutedEventArgs e)
{
//When used here, it just skippes everything in the method
//as i described on the comments in code above.
LoadPlaylists();
//after skipping the compiler comes here and tries to execute
//the lines below, which obviously causes exceptions because
above method was never completed to begin with.
var sd = playlistitems.Count;
//some more code
}

You should return the Task instead of void so that you can await for the method to complete.

Waiting on the results of GetGeopositionAsync()

I'm developing a WinPhone 8 App.
On this App there is a Button 'Send SMS'.
When the user clicks on this button two things should happen:
(Method A) Get the geo-coordinate of the current Location (using Geolocator and GetGeopositionAsync).
(Method B) Compose and send an SMS with the geo-coordinate as part of the body.
The Problem: GetGeopositionAsync is an asynchronous method. Before the coordinate is detected (which takes a few seconds) the SMS is sent (of course with no coordinates).
How can I tell Method 2 to wait until the coordinates are available?
OK, here is my code:
When the user presses the button, the coordinates are determined by the first method and the second method sends the SMS which includes the coordinates in its body:
private void btnSendSms_Click(object sender, RoutedEventArgs e)
{
GetCurrentCoordinate(); // Method 1
// -> Gets the coordinates
SendSms(); // Method 2
// Sends the coordinates within the body text
}
The first method GetCurrentCoordinate() looks as follows:
...
private GeoCoordinate MyCoordinate = null;
private ReverseGeocodeQuery MyReverseGeocodeQuery = null;
private double _accuracy = 0.0;
...
private async void GetCurrentCoordinate()
{
Geolocator geolocator = new Geolocator();
geolocator.DesiredAccuracy = PositionAccuracy.High;
try
{
Geoposition currentPosition = await geolocator.GetGeopositionAsync(
TimeSpan.FromMinutes(1),
TimeSpan.FromSeconds(10));
lblLatitude.Text = currentPosition.Coordinate.Latitude.ToString("0.000");
lblLongitude.Text = currentPosition.Coordinate.Longitude.ToString("0.000");
_accuracy = currentPosition.Coordinate.Accuracy;
MyCoordinate = new GeoCoordinate(
currentPosition.Coordinate.Latitude,
currentPosition.Coordinate.Longitude);
if (MyReverseGeocodeQuery == null || !MyReverseGeocodeQuery.IsBusy)
{
MyReverseGeocodeQuery = new ReverseGeocodeQuery();
MyReverseGeocodeQuery.GeoCoordinate = new GeoCoordinate(
MyCoordinate.Latitude,
MyCoordinate.Longitude);
MyReverseGeocodeQuery.QueryCompleted += ReverseGeocodeQuery_QueryCompleted;
MyReverseGeocodeQuery.QueryAsync();
}
}
catch (Exception)
{ // Do something }
}
private void ReverseGeocodeQuery_QueryCompleted(object sender,
QueryCompletedEventArgs<IList<MapLocation>> e)
{
if (e.Error == null)
{
if (e.Result.Count > 0)
{
MapAddress address = e.Result[0].Information.Address;
lblCurrAddress.Text = address.Street + " " + address.HouseNumber + ",\r" +
address.PostalCode + " " + address.City + ",\r" +
address.Country + " (" + address.CountryCode + ")";
}
}
}
}
And the Methode 'SendSms()':
private void SendSms()
{
SmsComposeTask smsComposeTask = new SmsComposeTask();
smsComposeTask.To = "0123456";
smsComposeTask.Body = "Current position: \rLat = " + lblLatitude.Text +
", Long = " + lblLongitude.Text +
"\r" + lblCurrAddress.Text;
// -> The TextBoxes are still empty!
smsComposeTask.Show();
}
The problem is, that all these TextBoxes (lblLatitude, lblLongitude, lblCurrAddress) are still empty when the method SendSms() sets the SmsComposeTask object.
I have to ensure that the TextBoxes are already set BEFORE the method SendSms() starts.

You should almost never mark a method async void unless it's a UI event handler. You're calling an asynchronous method without waiting for it to end. You are basically calling those 2 methods in parallel, so it's clear why the coordinates aren't available.
You need to make GetCurrentCoordinate return an awaitable task and await it, like this:
private async Task GetCurrentCoordinateAsync()
{
//....
}
private async void btnSendSms_Click(object sender, RoutedEventArgs e)
{
await GetCurrentCoordinateAsync();
// You'll get here only after the first method finished asynchronously.
SendSms();
}

This is one of the primary reasons you should avoid async void. void is a very unnatural return type for async methods.
First, make your GetCurrentCoordinate an async Task method instead of async void. Then, you can change your click handler to look like this:
private async void btnSendSms_Click(object sender, RoutedEventArgs e)
{
await GetCurrentCoordinate();
SendSms();
}
Your click handler is async void only because event handlers have to return void. But you should really strive to avoid async void in all other code.

There two things you're doing wrong here:
Using void returning async methods when you need to await on them. This is bad because you can't await on execution of these methods and should only be used when you can't make the method return Task or Task<T>. That's why you're not seeing anything on the text boxes when SendSmsis called.
Mixing UI and non-UI code. You should transfer data between UI and non-UI code to avoid tight coupling between code with different responsibilities. IT also makes it easy to read and debug the code.
ReverseGeocodeQuery does not have an awaitable async API but you can easily make your own:
private async Task<IList<MapLocation>> ReverseGeocodeQueryAsync(GeoCoordinate geoCoordinate)
{
var tcs = new TaskCompletionSource<IList<MapLocation>>();
EventHandler<QueryCompletedEventArgs<IList<MapLocation>>> handler =
(s, e) =>
{
if (e.Cacelled)
{
tcs.TrySetCancelled();
}
else if (e.Error != null)
{
tcs.TrySetException(e.Error);
}
else
{
tcs.TrySetResult(e.Result);
}
};
var query = new ReverseGeocodeQuery{ GeoCoordinate = geoCoordinate };
try
{
query.QueryCompleted += handler;
query.QueryAsync();
return await tcs.Task;
}
finally
{
query.QueryCompleted -= handler;
}
}
This way you'll get full cancellation and error support.
Now let's make the retrieval of the geo coordinate information all in one chunk:
private async Task<Tuple<Geocoordinate, MapLocation>> GetCurrentCoordinateAsync()
{
try
{
var geolocator = new Geolocator
{
DesiredAccuracy = PositionAccuracy.High
};
var currentPosition = await geolocator.GetGeopositionAsync(
TimeSpan.FromMinutes(1),
TimeSpan.FromSeconds(10))
.ConfigureAwait(continueOnCapturedContext: false);
var currentCoordinate = currentPosition.Coordinate;
var mapLocation = await this.ReverseGeocodeQueryAsync(
new GeoCoordinate(
currentCoordinate.Latitude,
currentCoordinate.Longitude));
return Tuple.Create(
currentCoordinate,
mapLocation.FirstOrDefault());
}
catch (Exception)
{
// Do something...
return Tuple.Create(null, null);
}
}
Now the button eventnt handler becomes much more readable:
private void btnSendSms_Click(object sender, RoutedEventArgs e)
{
var info = await GetCurrentCoordinate();
if (info.Item1 != nuil)
{
lblLatitude.Text = info.Item1.Latitude.ToString("0.000");
lblLongitude.Text = info.Item1.Longitude.ToString("0.000");
}
if (info.Item2 != null)
{
var address = info.Item2.Information.Address;
lblCurrAddress.Text = string.Format(
"{0} {1},\n{2} {3},\n{4} ({5})",
address.Street,
address.HouseNumber,
address.PostalCode,
address.City,
address.Country,
address.CountryCode);
}
SendSms(info.Item1, info.Item2);
}
Does this make sense?