C# 7 and .NET Core 2.0 High Performance

Parameters

The out and ref parameters are not allowed as parameters in the method signature. If multiple values need to be returned, tuples or a custom data structure can be used. The method should always return Task or Task<TResult>, as discussed previously.

Here are a few signatures for both synchronous and asynchronous methods:

Synchronous method	Asynchronous method
Void Execute();	Task ExecuteAsync();
List<string> GetCountries();	Task<List<string>> GetCountriesAsync();
Tuple<int, string> GetState(int stateID);	Task<Tuple<int, string>> GetStateAsync(int stateID);
Person GetPerson(int personID);	Task<Person> GetPersonAsync(int personID);