I would suggest you to have a look through these articles and this one in particular. The way to go here is write a LINQ query like so:
var filteredPeople = datasource.Where(x => !selectedPeople.Select(y => y.PersonID).Contains(x.PersonID));
This is assuming your type is Person and id has an identity field PersonID, datasource being the list of people you filter and selectedPeople the ones you do not want to show.
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