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How do you actually use FolderPicker in a UWP to grant IO access

I'm trying to do some generic database stuff with a UWP at a directory the user specifies, but I am having a nightmare with the access rights.
I've read everything I can find about the folder picker and I'm still not getting gifted access. My understanding was once the user picked a folder I could use that folder as I pleased, but it doesn't seem to be the case.
Is it as simple as I can't use Directory commands from a UWP?
Is there any documentation to show how to use FolderPicker Queries?
Am I going to have the same nightmare when I try an SQL connection?
private Windows.Storage.StorageFolder _fileAccess = null;
private async void Btn_Browse_Click(object sender, RoutedEventArgs e)
{
FolderPicker picker = new FolderPicker
{
ViewMode = PickerViewMode.List,
SuggestedStartLocation = PickerLocationId.ComputerFolder
};
picker.FileTypeFilter.Add("*");
_fileAccess = await picker.PickSingleFolderAsync();
if (_fileAccess == null)
{
return;
}
Tbx_Directory.Text = _fileAccess.Path;
StorageApplicationPermissions.FutureAccessList.
AddOrReplace("PickedFolderToken", _fileAccess);
string[] dataBases = Directory.GetFiles(_fileAccess.Path, #"*.db");
foreach (string file in dataBases ?? Enumerable.Empty<string>())
{
LBxV_Databases.Items.Add(file);
}
}
I get the access violation on the Directory use.

You are using FutureAccessList, this is a great choice, but there is a problem with the way you use it.
Here is the way to get the saved StorageFolder:
public async Task<StorageFolder> GetFolderFromAccessList(string tokenName)
{
var folder = await StorageApplicationPermissions.FutureAccessList.GetFolderAsync(tokenName);
return folder;
}
With the FolderPicker, you can get the StorageFolder object. But saving this object to the FutureAccessList does not allow you to access the folder with the path. You can only get the saved folder object by the Token which save in the FutureAccessList.
Because the UWP application is a sandbox application, when you access the database, I recommend that you save the database file in the application's local directory, such as ApplicationData.LocalFolder. You can't directly access the external file without adding special Capability.
You can find an official application example provided by Microsoft here, which demonstrates how to access files/folders persistently.
Best regards.

System.UnauthorizedAccessException when writing to the install path

I'm trying to download multiple files from an SFTP server and save them to the install path (or actually, ANY path at the moment just to get it working). However, I get an UnauthorizedAccess Exception no matter where I try to save the files.
As far as was aware, there are no special permissions required to save files to the install dir (Hence why I chose this folder).
Thread myThread = new Thread(delegate() {
string host;
string username;
string password;
// Path to folder on SFTP server
string pathRemoteDirectory = "public_html/uploads/17015/";
// Path where the file should be saved once downloaded (locally)
StorageFolder localFolder = Windows.ApplicationModel.Package.Current.InstalledLocation;
string pathLocalDirectory = localFolder.Path.ToString();
var methods = new List<AuthenticationMethod>();
methods.Add(new PasswordAuthenticationMethod(username, password));
//TODO - Add SSH Key auth
var con = new ConnectionInfo(host, 233, username, methods.ToArray());
using (SftpClient sftp = new SftpClient(con))
{
try
{
sftp.Connect();
var files = sftp.ListDirectory(pathRemoteDirectory);
// Iterate over them
foreach (SftpFile file in files)
{
Console.WriteLine("Downloading {0}", file.FullName);
using (Stream fileStream = File.OpenWrite(Path.Combine(pathLocalDirectory, file.Name)))
{
sftp.DownloadFile(file.FullName, fileStream);
Debug.WriteLine(fileStream);
}
}
sftp.Disconnect();
}
catch (Exception er)
{
Console.WriteLine("An exception has been caught " + er.ToString());
}
}
});
Connection to the server is all fine, the exception occurs on this line.
using (Stream fileStream = File.OpenWrite(Path.Combine(pathLocalDirectory, file.Name)))
I'm must be missing something obvious here but it's worth noting that I've also tried writing to Special Folders like the Desktop, the users Document folder and also direct to the C:/ drive, all with the same exception. I'm also running with Administrator privileges and I have the correct permissions set in the folders.

It turns out that SFTP was counting '.' and '..' as files and trying to download those, when obviously '.' is the set SFTP folder and '..' is the previous folder. This was causing a permissions exception, not 100% sure why. Simply iterating over the files to make sure they're not named '.' or '..' fixed the issue. Code below.
sftp.Connect();
var files = sftp.ListDirectory(pathRemoteDirectory);
// Iterate over them
foreach (SftpFile file in files)
{
if (!file.IsDirectory && !file.IsSymbolicLink)
{
using (Stream fileStream = File.OpenWrite(Path.Combine(pathLocalDirectory, file.Name)))
{
sftp.DownloadFile(file.FullName, fileStream);
Debug.WriteLine(pathLocalDirectory);
}
}
else if (file.Name != "." && file.Name != "..")
{
Debug.WriteLine("Directory Ignored {0}", file.FullName);
}
else if (file.IsSymbolicLink)
{
Debug.WriteLine("Symbolic link ignored: {0}", file.FullName);
}
}
sftp.Disconnect();

You have multiple problems here. The parent folder ("..") reference you answered is one blocker, but that doesn't address the deeper problem that the InstalledLocation is read-only.
UWP apps do not have direct access to most file system locations. By default they can read and write to their ApplicationData directory and they can read from (but not write to) the InstalledLocation. The failures you saw for Desktop, Documents, and C:\ are all expected.
Other locations (including Desktop, Documents, and C:) may be granted access by the user either explicitly or via the app's declared capabilities. They can be accessed via the file broker through the StorageFile object.
See the UWP File access permissions documentation:
The app's install directory is a read-only location. You can't gain
access to the install directory through the file picker.
For the long term you'll want to download your files somewhere else: probably into one of the ApplicationData folders. These folders are the only ones with no special permission requirements for UWP apps.
So why does this work for you now?
You're running into a debugging quirk where your app is not fully installed but is staged from your VS project directory. This allows the app to write to the staged install directory, but once it is properly deployed into Program Files\WindowsApps writing to the InstalledLocation will fail.

Try Path.GetTempPath();. You should have permission there.
When it says you don't have permission, you don't. 8-)
Also, there's no such thing as "no special permissions". Everything requires some level of permission for access.

Creating Files and Folders in UWP

Ive looked at at so many stackoverflow posts and articles but still didnt manage to create a file in UWP. In WPF it was really easy but UWP works differently.
I added the following in my manifest file:
<Capabilities>
<uap:Capability Name="documentsLibrary" />
</Capabilities>
Now im not sure what to do next. Inside my documents folder I have a subfolder named "Project Files". I want to create folders and files in there. How is this done in UWP? I really dont understand.

As microsoft states in their docs, its recommenced not to use the documents Library through an UWP app, instead opt for the built in storage unless its absolutely necessary.
There is an easy way to get around that if you use a folder picker
private async void buttonClick(){
FolderPicker folderPicker = new FolderPicker();
folderPicker.SuggestedStartLocation = PickerLocationId.DocumentsLibrary;
folderPicker.FileTypeFilter.Add("*");
StorageFolder folder= await folderPicker.PickSingleFolderAsync();
if (folder != null) {
// do Things On Folder
}
else
{
MessageDialog dialog = new MessageDialog("you selected nothing");
await dialog.ShowAsync();
}
}
The above opens up a folder select dialog, it returns the folder the user picked, its the recommended way for accessing locations outside your app's folder.
Here is how to Create a new file in this folder:
string name ="myTitle.txt";
await folder.CreateFileAsync(name, CreationCollisionOption.GenerateUniqueName);
here is how to open and write a file:
try {
StorageFile myFile = await folder.GetFileAsync(name);
await Windows.Storage.FileIO.WriteTextAsync(myFile, "myStringContent");
}
catch (Exception e)
{
Debug.WriteLine("Failure: "+e.Message);
return;
}
remember you can always avoid opening up a dialog if you use the local storage instead, it returns you app's storage folder in one line, like this:
var folder= ApplicationData.Current.LocalFolder;

I believe in UWP using the documents library is neither recommended or permitted. See https://blogs.msdn.microsoft.com/wsdevsol/2013/05/09/dealing-with-documents-how-not-to-use-the-documentslibrary-capability-in-windows-store-apps/
If you side load the app and use the documents library capability the app gets access only to declared file types, not to everything in documents.
See https://msdn.microsoft.com/en-us/library/windows/apps/hh464936.aspx#special_capabilities
Note that this special capability will not let you pass through app certification in Store, unless you go through some special procedure contacting MS first.
To create folder, use StorageFolder. To create file, use StorageFile.
See https://learn.microsoft.com/en-us/windows/uwp/files/quickstart-reading-and-writing-files

Xamarin media plugin get android image path

I am using the media plugin for xamarin forms (by james montemagno) and the actual taking of the picture and storing it works fine, I have debugged the creation of the image on the emulator and it is stored in
/storage/emulated/0/Android/data/{APPNAME}.Android/files/Pictures/{DIRECTORYNAME}/{IMAGENAME}
however in my app it will get a list of file names from an API I want to check if the image exists in that folder.
The following works fine on IOS
var documentsDirectory = Environment.GetFolderPath(Environment.SpecialFolder.Personal);
string jpgFilename = System.IO.Path.Combine(documentsDirectory, App.IMAGE_FOLDER_NAME);
jpgFilename = System.IO.Path.Combine(jpgFilename, name);
I have tried the 2 following methods for getting it on android but both are incorrect
var documentsDirectory = System.Environment.GetFolderPath(System.Environment.SpecialFolder.Personal);
string jpgFilename = System.IO.Path.Combine(documentsDirectory, App.IMAGE_FOLDER_NAME);
jpgFilename = System.IO.Path.Combine(jpgFilename, name);
Java.IO.File dir = Android.OS.Environment.GetExternalStoragePublicDirectory(Android.OS.Environment.DataDirectory + "/" + App.IMAGE_FOLDER_NAME + "/" + name);
dir ends up as
/storage/emulated/0/data/{DIRECTORY}/{IMAGENAME}
jpgFileName ends up as /data/data/{APPNAME}.Android/files/{DIRECTORYNAME}/{IMAGENAME}
I dont want to hardcode anything in the paths but neither of these are right. I could not find anything in the GIT documentation for getting the file path except by looking at the path of the file created when taking a picture

The problem
I had the same kind of issue with Xamarin Media Plugin. For me, the problem is:
we don't really know where the plugin save the picture on android.
After reading all documentation I found, I just noted this:
... When your user takes a photo it will still store temporary data, but also if needed make a copy to the public gallery (based on platform). In the MediaFile you will now see a AlbumPath that you can query as well.
(from: Github plugin page)
so you can save your photo to your phone gallery (it will be public) but the path is known.
and we don't know what means "store the temporary data".
Solution
After investigating on how/where an app can store data, I found where the plugin stores photos on Android >> so I can generate back the full file names
In your Android app, the base path you are looking for is:
var basePath = Android.App.Application.Context.GetExternalFilesDir(null).AbsolutePath
It references your app's external private folder. It looks like that:
/storage/emulated/0/Android/data/com.mycompany.myapp/files
So finally to get your full file's path:
var fullPath = basePath + {DIRECTORYNAME} + {FILENAME};
I suggest you to make a dependency service, for instance 'ILocalFileService', that will expose this 'base path' property.
Please let me know if it works for you !

I resolved a similar problem. I wanted to collect all files for my app in a folder visible to all users.
var documentsDirectory = Android.OS.Environment.GetExternalStoragePublicDirectory(
Android.OS.Environment.DirectoryDocuments);
If you want to create Directory, add to your class using System.IO; and you have the same functions in a normal .NET application.
if (!Directory.Exists(path))
Directory.CreateDirectory(path);
If you want to create files or directory, you can use PCLStorage.
public async Task<bool> CreateFileAsync(string name, string context)
{
// get hold of the file system
IFolder folder = FileSystem.Current.LocalStorage;
// create a file, overwriting any existing file
IFile file = await folder.CreateFileAsync(name,
CreationCollisionOption.ReplaceExisting);
// populate the file with some text
await file.WriteAllTextAsync(context);
return true;
}

to get the private path
var privatePath = file.Path;
to get the public Album path
var publicAlbumPath = file.AlbumPath;
se the documentation here https://github.com/jamesmontemagno/MediaPlugin

ReadLinesAsync in UWP from absolute file path

I get error
The filename, directory name, or volume label syntax is incorrect. (Exception from HRESULT: 0x8007007B)
My code is
public async void ReadFile()
{
var path = #"F:\VS\WriteLines.xls";
var folder = Windows.ApplicationModel.Package.Current.InstalledLocation;
var file = await folder.GetFileAsync(path);
var readFile = await Windows.Storage.FileIO.ReadLinesAsync(file);
foreach (var line in readFile.OrderBy(line =>
{
int lineNo;
var success = int.TryParse(line.Split(';')[4], out lineNo);
if (success) return lineNo;
return int.MaxValue;
}))
{
itemsControl.Items.Add(line);
}
}
The error shows up at var file = await folder.GetFileAsync(path);

You cannot read a file from an arbitrary location on disk in a UWP App.
There are a couple of ways you can still accomplish your task:
You can add the WriteLines.xls file to your project and set it's build action to Content and Copy to output Directory to Copy if newer. You can then access the file with the code you have by simply replacing the "path" value to:
var path = #"WriteLines.xls"
More details here
If you need to be able to read any files from disk, you need to either use a FilePicker to select the file or copy the file in the Documents Folder and change the folder to:
var folder = KnownFolders.DocumentsLibrary;
More details here

You are asking for file with absolute path from application's local folder - hence it throws that error as you provide path that includes drive name.
In general UWP is very restrictive on where/how you can get files from - I don't think you can get it from absolute path in the sample (app needs more permissions to get to similar places). You can try StorageFile.GetFileFromPathAsync.
Detailed info on locations app can access - UWP apps on Windows 10: File access permissions.