<PackageReference Include="System.Reactive" Version="7.0.0-preview.1" />

System.Reactive.Disposables.SingleAssignmentDisposableValue

namespace System.Reactive.Disposables { public struct SingleAssignmentDisposableValue { public bool IsDisposed { get; } public IDisposable Disposable { get; set; } public void Dispose(); public static bool operator ==(SingleAssignmentDisposableValue left, SingleAssignmentDisposableValue right); public static bool operator !=(SingleAssignmentDisposableValue left, SingleAssignmentDisposableValue right); } }