Write into file from assets folder uwp - win-universal-app

Question

I'd like to write text content into a file that is located Assets folder, so I access file but I don't have access to write into it, my code is:
try {
//get the file
StorageFile storageFile = await StorageFile.GetFileFromApplicationUriAsync(new Uri("ms-appx:///assets/test.txt"));
//try to write sring to it
await FileIO.WriteTextAsync(storageFile, "my string");
} catch (Exception ex) {
Debug.WriteLine("error: " + ex);
}
and I get the error:
Exception thrown: 'System.UnauthorizedAccessException' in mscorlib.ni.dll
error: System.UnauthorizedAccessException: Access is denied. (Exception from HRESULT: 0x80070005 (E_ACCESSDENIED))
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.GetResult()
at MyProject.MainPage.<overWriteHtmlSrcFile>d__6.MoveNext()
Have to mention that I need to change this file due app scenario, or maybe is there a way to create this file in public app folder and then move it in assets.

Answer 1

Files located into Assets folder are read only that's why you get this exception. Like you mentioned at the end, there is a method to create your file in a public location, write what you need into it and then just move the file in assets folder. It will be like:
try {
//create file in public folder
StorageFolder storageFolder = ApplicationData.Current.LocalFolder;
StorageFile sampleFile = await storageFolder.CreateFileAsync("test.txt", CreationCollisionOption.ReplaceExisting);
//write sring to created file
await FileIO.WriteTextAsync(sampleFile, htmlSrc);
//get asets folder
StorageFolder appInstalledFolder = Windows.ApplicationModel.Package.Current.InstalledLocation;
StorageFolder assetsFolder = await appInstalledFolder.GetFolderAsync("Assets");
//move file from public folder to assets
await sampleFile.MoveAsync(assetsFolder, "new_file_name.txt", NameCollisionOption.ReplaceExisting);
} catch (Exception ex) {
Debug.WriteLine("error: " + ex);
}