Thanks. Yes - I had got this far myself. However, I'm don't see how you can use this approach to apply the chosen theme to all other opened forms using a pure MVVM approach. For example, if you chose "MaterialDark", you could save this to My.Settings. However, you can't use:
SfSkinManager.SetTheme(Application.Current.MainWindow, new Theme(SelectedTheme));
In other view models for other forms as there's no equivalent of Application.Current.MainWindow for other forms. You could use:
SfSkinManager.SetTheme(this, new Theme("MaterialDark"));
In the code behind the form, but this would be breaking the pure MVVM requirement, which I'm trying to avoid (i.e. I'm trying not to use any code behind the view at all.
Any more ideas??