<PackageReference Include="System.Reactive" Version="6.0.2" />

IEventPatternSource<TSender, TEventArgs>

public interface IEventPatternSource<TSender, TEventArgs>
Represents a data stream signaling its elements by means of an event.
using System.Runtime.CompilerServices; using Windows.Foundation; namespace System.Reactive { [System.Runtime.CompilerServices.NullableContext(1)] [CLSCompliant(false)] public interface IEventPatternSource<[System.Runtime.CompilerServices.Nullable(2)] TSender, [System.Runtime.CompilerServices.Nullable(2)] TEventArgs> { event TypedEventHandler<TSender, TEventArgs> OnNext; } }