You can use the following code for sorting.
data: lv_sort_order TYPE char1.
lv_sort_order = cl_bsp_wd_collection_wrapper=>sort_descending.
TRY.
me->typed_context->templatetext->collection_wrapper->sort( iv_attr_name = lv_attr_name
iv_sort_order = lv_sort_order).
CATCH cx_crm_cic_parameter_error.
ENDTRY.
Thanks,
Singla