//HIERARCHY LEVEL SELECTION - USER TO INITIALLY SELECT//
 //GROUP NAME = HIERARCHY//
 private void ComponentRB_Checked(object sender, RoutedEventArgs e)
 {
     //MUST CHECK IF USER HAS SELECTED A MODEL FROM Models_ComBox TO
     //DETERMINE IF CATEGORIES SHOULD BE RETRIEVED FROM GetPropertiesModel.GetSystemProperties
     if (Models_ComBox.SelectedItem != null)
     {
         ExportProperties.Selected_HierLvl = 3;
         GetPropertiesModel.GetSystemProperties(Models_ComBox.SelectedItem.ToString(), "Block");
         CatProp_ListView.ItemsSource = GetPropertiesModel.ReturnCategories;
     }
 }
        //CATEGORY LISTVIEW - USER TO INITIALLY SELECT//
        private void PropCat_Selection(object sender, SelectionChangedEventArgs e)
        {
            //CHECK PREVIOUS SELECTION IS NOT SAME AS CURRENT SELECTION
            GetPropertiesModel.ReturnProp.Clear();

            //UPDATES AVAILABLE PROPERTIES WHEN CATEGORY SELECTED IN CatProp_ListView
            var selectedCat = CatProp_ListView.SelectedItem as Category;

            if (selectedCat != null)  //INITIATES PROPERTIES RETRIEVEL WHEN CATEGORY SELECTED (CONTAINER NOT EMPTY)
                                      //OTHERWISE UPDATES CATEGORIES SINCE NO SelectedItem IS BOUND
            {
                //RESPECTS OBSERVABLE COLLECTION PROPERTIES
                GetPropertiesModel.GetCatProperties(selectedCat.CatName); //TAKES USER SELECTED CATEGORY TO RETRIEVE PROPERTIES
                ExportProperties.Selected_Cat = selectedCat.CatName;
                Prop_ListView.ItemsSource     = GetPropertiesModel.ReturnProp;
            }
        }
        //----------------------------------------------------------------------------------------------------------


        //MODEL FILES COMBO BOX - USER TO INITIALLY SELECT SPECIFIC HIERARCHY LEVEL//
        //WHEN NEW SELECTION MADE IN RADIO BUTTON GROUP, RETRIEVES AVAILABLE CATEGORIES (GetProertiesModel.cs)
        //& RELOADS IN CatProp_LISTVIEW
        //USES OBSERVABLE COLLECTION PROPERTIES.
        private void ModelCB_Select(object sender, SelectionChangedEventArgs e)
        {
            if (SystemRB.IsChecked == true && Models_ComBox.SelectedItem != null)
            {
                GetPropertiesModel.GetSystemProperties(Models_ComBox.SelectedItem.ToString(), "File");
                CatProp_ListView.ItemsSource = GetPropertiesModel.ReturnCategories;
            }
            else if (CatRB.IsChecked == true && Models_ComBox.SelectedItem != null)
            {
                GetPropertiesModel.GetSystemProperties(Models_ComBox.SelectedItem.ToString(), "Layer");
                CatProp_ListView.ItemsSource = GetPropertiesModel.ReturnCategories;
            }
            else if (ComponentRB.IsChecked == true && Models_ComBox.SelectedItem != null)
            {
                GetPropertiesModel.GetSystemProperties(Models_ComBox.SelectedItem.ToString(), "Block");
                CatProp_ListView.ItemsSource = GetPropertiesModel.ReturnCategories;
            }
        }