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PCLStorage NuGetPackage not allow creating folder or file on device

I have a problem with creating folder with nuget package PCLStorage, I cannot create folder.
Nothing appear inside my files folder. I,m using my device not emulator there is android version 8.0
public async Task WriteDataAsync(string filename, string data)
{
string folderName = "SignatureSotrage";
IFolder folder = FileSystem.Current.LocalStorage;
folder = await folder.CreateFolderAsync(folderName, CreationCollisionOption.ReplaceExisting);
}
Here is a code where I run this function:
public ICommand AddCustomerCommand => new Command(async () =>
{
Signature = await SignatureFromStream();
// Signature should be != null
var customer = new Customer()
{
FullName = this.FullName,
IsAccepted = this.IsAccepted,
Birthday = this.Birthday
};
if(Signature != null)
{
customer.Image = this.Signature.ToString();
}
else
{
await Application.Current.MainPage.DisplayAlert("Błąd", "Nie wszystkie pola zostały poprawnie wypełnione", "OK");
return;
}
await DependencyService.Get<IFileHelper>().WriteDataAsync("signature.txt", "this is file");
//_context.Customers.Add(customer);
//_context.SaveChanges();
});

did you debug your code & check if the file/folder is actually getting created by your code or else it enters the catch block and goes with the normal flow?
Check for UserPermissions every time for reading & write permission before doing any operations on the storage. You can add the Nugget packet Plugin.Permission it handles everything for you, it adds both the permission in the manifest.
For checking user permissions always try calling CheckForStoragePermissions() before performing any operations on storage.(*DialogService is CustomDialogBox)
if( !await CheckForStoragePermissions() )
{
DialogService.Alert("Invalid Permission", "User declined permission for this action");
return;
}
private async Task<bool> CheckForStoragePermissions()
{
PermissionStatus storagePermissionStatus = await CrossPermissions.Current.CheckPermissionStatusAsync(Permission.Storage);
if (storagePermissionStatus != PermissionStatus.Granted)
{
Dictionary<Permission, PermissionStatus> storagePermissionResult = await CrossPermissions.Current.RequestPermissionsAsync(Permission.Storage);
if (storagePermissionResult.ContainsKey(Permission.Storage))
{
storagePermissionStatus = storagePermissionResult[Permission.Storage];
}
}
return storagePermissionStatus == PermissionStatus.Granted;
}

I test the sample code on GitHub. https://github.com/dsplaisted/PCLStorage
Based on my test the folder path would like:
/data/user/0/PCLStorage.Test.Android/files/
It is a internal storage. You couldn't see the files without root permission. https://learn.microsoft.com/en-us/xamarin/android/platform/files/#working-with-internal-storage
If you want to see the files in internal storage, you could use adb tool. Please refer to the way in the link. How to write the username in a local txt file when login success and check on file for next login?

DisplayApplicationPicker not showing open with prompt

I'm creating a Xamarin Forms application (currently only UWP) where I want to open an PDF file from the local storage. In the UWP project I receive the file path form the Xamarin Portable Project. I use the following function to open the Open With Prompt.
public void OpenFileWith(string path)
{
Task.Run(async () =>
{
var file = await StorageFile.GetFileFromPathAsync(path);
if (file != null)
{
var options = new LauncherOptions();
options.DisplayApplicationPicker = true;
var success = await Launcher.LaunchFileAsync(file, options);
if (success)
{
//File Launched
}
else
{
//File Launch Failed
}
}
});
}
I think I've done everything correct according to the Documentation. When I don't add the LauncherOptions the file opens correctly in the default selected Application.
Is there something I'm missing. Permissions maybe? I know the documentation has a remark "This property is only implemented on Desktop devices.". I'm testing on a Desktop (Windows 10 via VMWare)

This should work:
public async Task OpenFileWithAsync(string path)
{
var file = await StorageFile.GetFileFromPathAsync(path);
if (file != null)
{
var options = new LauncherOptions();
options.DisplayApplicationPicker = true;
var success = await Launcher.LaunchFileAsync(file, options);
if (success)
{
//File Launched
}
else
{
//File Launch Failed
}
}
}
Call:
await OpenFileWithAsync(...);

Xamarin C# android and PARSE - Downloading a parseFile inside a parseObject

I previously made a post asking how to send a .3gpp audio file up to the parse cloud here:
Xamarin C# Android - converting .3gpp audio to bytes & sending to parseObject
I have managed to do this successfully, on parse's data manager, I can click the file's link and play the sound sent from my android device successfully.
Here's the code for uploading the data to the cloud:
async Task sendToCloud(string filename)
{
ParseClient.Initialize ("Censored Key", "Censored Key");
string LoadPath = System.Environment.GetFolderPath(System.Environment.SpecialFolder.ApplicationData);
string savetheFile = sName + ".3gpp";
string tempUserName;
LoadPath += savetheFile;
Console.WriteLine ("loadPath: " + LoadPath);
try
{
byte[] data = File.ReadAllBytes(LoadPath);
ParseFile file = new ParseFile(savetheFile, data);
await file.SaveAsync();
var auidoParseObject = new ParseObject("AudioWithData");
//Console.WriteLine(ParseUser.getUserName());
if (ParseUser.CurrentUser != null)
{
tempUserName = ParseUser.CurrentUser.Username.ToString();
}
else{
tempUserName = "Anonymous";
}
//tempUserName = ParseUser.CurrentUser.Username.ToString();
Console.WriteLine("PARSE USERNAME: " + tempUserName);
auidoParseObject["userName"] = tempUserName;
auidoParseObject["userName"] = tempUserName;
auidoParseObject["file"] = file;
await auidoParseObject.SaveAsync();
}
catch (Exception e)
{
Console.WriteLine("Failed to await audio object! {0}" + e);
}
}
So as you can see, I'm sending a ParseObject called "AudioWithData".
This object contains two children:
-The username of the user who uploaded the file (string)
-The parseFile called "file" (which has the following two children)
---SaveTheFile (A string containing the name of the audio file, input by the user, with the .3gpp extension added on the end, for example "myAudioFile.3gpp"
---data (this contains the bytes of the audio file)
I need to be able to download the file onto my android device, and play it through a mediaplayer object.
I've checked over the documentation on the parse website, but I haven't managed to do this:
(excuse my pseudo querying syntax here)
SELECT (audio files) FROM (the parseObject) WHERE (the username = current user)
I then, eventually, want to place all of these files into a listview, and when the user clicks the file, it plays the audio.
I've tried the following but I don't really know what I'm doing with it...
async Task RetrieveSound(string filename)
{
ParseClient.Initialize ("Censored key", "Censored key");
Console.WriteLine ("Hit RetrieveSound, filename = " + filename);
string username;
var auidoParseObject = new ParseObject("AudioWithData");
if (ParseUser.CurrentUser != null) {
username = ParseUser.CurrentUser.Username.ToString ();
} else {
username = "Anonymous";
}
string cloudFileName;
Console.WriteLine ("username set to: " + username);
var HoldThefile = auidoParseObject.Get<ParseFile>("audio");
//fgher
var query = from audioParseObject in ParseObject.GetQuery("userName")
where audioParseObject.Get<String>("userName") == username
select file;
IEnumerable<ParseFile> results = await query.FindAsync();
Console.WriteLine ("passed the query");
//wfojh
byte[] data = await new HttpClient().GetByteArrayAsync(results.Url);
Console.WriteLine ("putting in player...");
_player.SetDataSourceAsync (data);
_player.Prepare;
_player.Start ();
}
Any help would be GREATLY APPRECIATED! Even a point in the right direction would be great!
Thanks!
EDIT--
I'm actually getting a query error on the following lines
(I can't post images because of my reputation - I lost access to my main stackOverflow account :/ )
Links to images here:
first error: http://i.stack.imgur.com/PZBJr.png
second error: http://i.stack.imgur.com/UkHvX.png
Any ideas? The parse documentation is vague about this.

this line will return a collection of results
IEnumerable<ParseFile> results = await query.FindAsync();
you either need to iterate through them with foreach, or just pick the first one
// for testing, just pick the first one
if (results.Count > 0) {
var result = results[0];
byte[] data = await new HttpClient().GetByteArrayAsync(result.Url);
File.WriteAllBytes(some_path_to_a_temp_file, data);
// at this point, you can just initialize your player with the audio file path and play as normal
}

Windows Store App, ... cannot be used on the current platform. ERROR

I have Windows Store app which is actually a game and I'm trying to implement posting result on Facebook.
I'm using Facebook SDK for .Net from facebooksdk.net
Here's my code
FacebookSession session = await App.FacebookSessionClient.LoginAsync("publish_stream");
if (session == null)
{
MessageDialog dialog = new MessageDialog("Error while getting publishing permissions. Please try again.");
await dialog.ShowAsync();
return;
}
// refresh your access token to contain the publish permissions
App.AccessToken = session.AccessToken;
FacebookClient fb = new FacebookClient(App.AccessToken);
string message = "Your score is: " + points;
dynamic proba = message;
try
{
//The next line throws exception
dynamic fbPostTaskResult = await fb.PostTaskAsync("/me/feed?message='{0}", proba);
var result = (IDictionary<string, object>)fbPostTaskResult;
var successMessageDialog = new Windows.UI.Popups.MessageDialog("Posted Open Graph Action, id: " + (string)result["id"]);
await successMessageDialog.ShowAsync();
}
catch (Exception ex)
{
MessageDialog exceptionMessageDialog = new MessageDialog("Exception during post: " + ex.Message);
exceptionMessageDialog.ShowAsync();
}
And the Exception Message that I recieve is:
The API 'System.String.Get_FirstChar()' cannot be used on the current platform. See http://go.microsoft.com/fwlink/?LinkId=248273 for more information
I tried diffrent ways to send arguments to "PostTaskAsync()" method but I always got the same Exception. Searching Google and Stackoverflow wasn't much helpful.
I'm much grateful for any sort of help.
Cheers

C# Windows Store App - File IO using async/await causes timeouts and InvalidOperationException

this is my first post on this site and I searched high and wide to get my code to work.
Like the title says, it's a WinRT App and I'm having difficulty with File IO. What I want to do is read in a text file stored in a folder that is inside the application installation directory and that contains lines of data that I'll feed into an List<>.
public static async void GetStations()
{
try
{
using (var stream = await Windows.Storage.ApplicationData.Current.LocalFolder.OpenStreamForReadAsync(#"MyApp\Data\file.txt"))
{
using (var streamReader = new StreamReader(stream))
{
while (streamReader.Peek() >= 0)
{
string line = await streamReader.ReadLineAsync();
//do something with
}
}
}
}
catch (Exception e)
{
...
}
finally
{
...
}
}
the problem is I am getting file not found errors when trying to run it. Can anyone help? If you require that I post more information, I can...
Thanks in advance.

If you are distributing your file as a part of your application package then Package.Current.InstalledLocation is the right location. ApplicationData.Current.LocalFolder contains only files that have been put there by your application.
The correct code would be:
public static async void GetStations()
{
try
{
using (var stream = await Windows.ApplicationModel.Package.Current.InstalledLocation.OpenStreamForReadAsync(#"Data\file.txt"))
{
using (var streamReader = new StreamReader(stream))
{
while (streamReader.Peek() >= 0)
{
string line = await streamReader.ReadLineAsync();
//do something with
}
}
}
}
catch (Exception e)
{
//...
}
finally
{
//...
}
}
The file must be included in you project inside Data folder and have Build Action set to Content.

Instead of opening from ApplicationData, you probably need:
Windows.ApplicationModel.Package.Current.InstalledLocation.GetFileAsync
This will get the file in the package's installation folder, instead of the Application's Data folder.