Rename class 'YoutubeAPIHelper' to match pascal case naming rules, consider using 'YoutubeApiHelper'. (https://rules.sonarsource.com/csharp/RSPEC-101)

Assign this magic number '50' to a well-named variable or constant, and use that instead. (https://rules.sonarsource.com/csharp/RSPEC-109)

Add the 'Async' suffix to the name of this method. (https://rules.sonarsource.com/csharp/RSPEC-4261)

Add a 'protected' constructor or the 'static' keyword to the class declaration. (https://rules.sonarsource.com/csharp/RSPEC-1118)

Remove this default value assigned to parameter 'nullable'. (https://rules.sonarsource.com/csharp/RSPEC-3254)

Remove this default value assigned to parameter 'nullable'. (https://rules.sonarsource.com/csharp/RSPEC-3254)

Remove this default value assigned to parameter 'nullable'. (https://rules.sonarsource.com/csharp/RSPEC-3254)

Possible null reference assignment.

Possible null reference assignment.

Non-nullable field 'API_KEY' must contain a non-null value when exiting constructor. Consider adding the 'required' modifier or declaring the field as nullable.

Possible null reference assignment.

Possible null reference assignment.

Non-nullable field 'API_KEY' must contain a non-null value when exiting constructor. Consider adding the 'required' modifier or declaring the field as nullable.

Non-nullable field 'PLAYLIST_ID' must contain a non-null value when exiting constructor. Consider adding the 'required' modifier or declaring the field as nullable.

Dereference of a possibly null reference.

Possible null reference return.

Dereference of a possibly null reference.

Possible null reference return.

This async method lacks 'await' operators and will run synchronously. Consider using the 'await' operator to await non-blocking API calls, or 'await Task.Run(...)' to do CPU-bound work on a background thread.