Explain user what is happening

TryAccessLibraryAsyncMessageDialog.cs

//explain the issue
MessageDialog requestPermissionDialog =
    new MessageDialog($"The app needs to access the {library}. " +
                      "Press OK to open system settings and give this app permission. " +
                      "If the app closes, reopen it afterwards. " +
                      "If you Cancel, the app will have limited functionality only.");

//setup dialog commands
var okCommand = new UICommand("OK");
requestPermissionDialog.Commands.Add(okCommand);
var cancelCommand = new UICommand("Cancel");
requestPermissionDialog.Commands.Add(cancelCommand);
requestPermissionDialog.DefaultCommandIndex = 0;
requestPermissionDialog.CancelCommandIndex = 1;

//display to user
var requestPermissionResult = await requestPermissionDialog.ShowAsync();