So If we have IEnumerable as parameter of any method, we can pass any collection types to the function. Ie we gönül have method to operate on abstraction not any specific implementation. What this code is saying is that if userId was specified, then add a filter on the data https://finnmwfls.wikifiltraciones.com/3069834/en_son_beş_c_ienumerable_nasıl_kullanılır_kentsel_haber