public static void Show(Type viewModelType)
        {
            var targetDialog = OpenDialogMappings.Where(d => d.Value == viewModelType).Select(d => d.Key).FirstOrDefault();

            if (targetDialog != null)
            {
                targetDialog.Show();
            }
        }
        public static void CloseDialog(Type viewModelType)
        {
            var targetDialog = OpenDialogMappings.Where(d => d.Value == viewModelType).Select(d => d.Key).FirstOrDefault();

            if (targetDialog != null)
            {
                targetDialog.Close();
                OpenDialogMappings.Remove(targetDialog);
            }
        }