Drop Down field using same table data

I have scaffolded some models, one of which is for staff. When I add a new staff member, there is a free text field for the managers ID, which will be the id of their manager in the same database table. Also in this table/model, I have a boolean field to say if the person is a manager. What I would like is to replace the free text field for managers ID with a drop down of the names in the staff table that have the manager flag set to true. I have created a method that returns a list of the managers from the staff table but I can't seem to get it to populate a drop down. What would be the best way to achieve this?

If you have a method that gets this data just invoke it and assign it to a page field. Then set the Data property of your dropdown to that list.

For inspiration you can check a CRUD page generated for an entity that has a foreign key. Radzen Blazor Studio generates lookup dropdowns that are populated in a similar way.