Validating a Nuget API Key using the Nuget.Core API

I am looking to validate Nuget feeds API Key using the Nuget.Core c# API.

example:

//Coect to the official package repository
var repo = PackageRepositoryFactory.Default.CreateRepository(environment.FeedUrl);

//Get the list of all NuGet packages with ID 'EntityFramework'       
List<IPackage> packages = repo.GetPackages().ToList();

//Retu nuget packages.
retu packages.Select(x=>x.GetFullName()).ToList();

What is the easiest way to test an API Key without being destructive?