✅ Getting data from api on app startup?

I am experimenting with a very simple app. I want to keep a list of pokemon that I get from an api in a variable so that when a user searches in the front end for a name, the dotnet api will search do a string search on this list for similar names and return to the client to be rendered in a typeahead. Not sure how to make my api make an "automatic" http request for data without user interaction