Share File Between Applications - raspberry-pi3

Question

I am developing a reasonably complex process control background application on a Pi 3 (using c#, VC 2015). This is being developed and tested in a modular manner (display, user input, gpio extender boards, various types of sensors, relays, network comms, etc). Each module is built as a separate DLL and tested with its own background test app.
My problem is that I need to maintain a common set of data across all modules, particularly a set of application parameters. Also local storage as a cache for results and logging. So several different applications need to access this data during development - but only one at a time. Obviously in the final project, there will be a single application, so no problem.
I have been amazed to find that Win IoT does not seem to allow a simple file to be accessible to different applications. App Services and other inter-app communications all seem to be at the transaction level and not appropriate here. To build an app services facility to handle all I/o would be tedious(not ultimately required).
Does anyone have an idea as to how this situation could be managed sensibly, please?

Answer 1

Due to File access permissions of UWP app. Reading data from a file in local storage seems unreachable.
So, if you are willing to use a removable device(external storage) attached to the Raspberry Pi and store your application parameters in a file, like a text file, and read the data from your apps.
I test the following code(UWP app) on desktop and read data successfully from multi apps. I am sure that you can read data on Raspberry Pi from one app but I didn't test multi apps. You can have a try. If there is any concern please feel free let me know.
Task.Run( async () =>
{
var removableDevices = KnownFolders.RemovableDevices;
var externalDrives = await removableDevices.GetFoldersAsync();
var drive0 = externalDrives[0];
var testFolder = await drive0.GetFolderAsync("test");
var SharedDateFile = await testFolder.GetFileAsync("data.txt");
var data = await FileIO.ReadTextAsync(SharedDateFile);
System.Diagnostics.Debug.WriteLine(data);
});
In the app manifest, you need specify the Removable Storage capability and register at least one File Type Association declaration.
UPDATE:
Using publisher folder is the better solution. First, add the following extension in Package.appxmanifest:
<Extensions>
<Extension Category="windows.publisherCacheFolders">
<PublisherCacheFolders>
<Folder Name="Folder1"/>
</PublisherCacheFolders>
</Extension>
</Extensions>
Then write and read file like this:
//Write file
var folder = Windows.Storage.ApplicationData.Current.GetPublisherCacheFolder("Folder1");
var file = await folder.CreateFileAsync("settings.txt", Windows.Storage.CreationCollisionOption.OpenIfExists);
await FileIO.WriteTextAsync(file,"Hello writen by app1");
//Read file
var folder = Windows.Storage.ApplicationData.Current.GetPublisherCacheFolder("Folder1");
var file = await folder.GetFileAsync("settings.txt");
var text = await FileIO.ReadTextAsync(file);
System.Diagnostics.Debug.WriteLine(text);