public void ChooseScriptSources() { const string Separator = @";"; var chooserMessage = new FileChooserMessage(); if (IncludeFile == null) { IncludeFile = ""; } chooserMessage.SelectedFiles = IncludeFile?.Split(Separator.ToCharArray()); chooserMessage.PropertyChanged += (sender, args) => { if (args.PropertyName == @"SelectedFiles") { if (chooserMessage.SelectedFiles != null) { if (string.IsNullOrEmpty(IncludeFile)) { IncludeFile = string.Join(Separator, chooserMessage.SelectedFiles); } else { IncludeFile += Separator + string.Join(Separator, chooserMessage.SelectedFiles); } } } }; _eventPublisher.Publish(chooserMessage); }