SerialDisposableValue
Represents a disposable resource whose underlying disposable resource can be replaced by another disposable resource, causing automatic disposal of the previous underlying disposable resource.
            
                using System.Runtime.CompilerServices;
using System.Threading;
namespace System.Reactive.Disposables
{
    [System.Runtime.CompilerServices.NullableContext(2)]
    [System.Runtime.CompilerServices.Nullable(0)]
    internal struct SerialDisposableValue : ICancelable, IDisposable
    {
        private IDisposable _current;
        public bool IsDisposed => Volatile.Read(ref _current) == BooleanDisposable.True;
        public IDisposable Disposable {
            get {
                return System.Reactive.Disposables.Disposable.GetValue(ref _current);
            }
            set {
                System.Reactive.Disposables.Disposable.TrySetSerial(ref _current, value);
            }
        }
        [System.Runtime.CompilerServices.NullableContext(1)]
        public bool TrySetFirst(IDisposable disposable)
        {
            return System.Reactive.Disposables.Disposable.TrySetSingle(ref _current, disposable) == TrySetSingleResult.Success;
        }
        public void Dispose()
        {
            System.Reactive.Disposables.Disposable.Dispose(ref _current);
        }
    }
}