public MaterialManageViewModel(BaseViewModel parent)
{
this.parent = parent;
// Get the list of all active materials
materialList = MaterialModel.getMaterialList();
// Get list of all deleted materials
deletedMaterialList = MaterialModel.getDeletedMaterialList();
// Keep a copy of the materialList so that we can restore the list after filtering
originalMaterialList = new ObservableCollection <MaterialModel>(materialList);
}