<PackageReference Include="System.Reactive" Version="4.2.0-preview.625" />
IObserver<TValue, TResult>
Provides a mechanism for receiving push-based notifications and returning a response.
namespace System.
Reactive
{
public interface IObserver<
in TValue,
out TResult>
{
TResult OnNext(
TValue value);
TResult OnError(
Exception exception);
TResult OnCompleted();
}
}