ReactivePropertyで2度押し防止

Rxのお勉強。もっと良い実装あったら教えてください。

    public class MainVM
    {
        public readonly ObservableCollection<string> Messages = new ObservableCollection<string>();

        public MainVM()
        {
            IsBusy = new ReactiveProperty<bool>(false);
            Input = new ReactiveProperty<string>("");
            TestCommand =
                IsBusy.CombineLatest(Input, (busy, input) => !busy && !string.IsNullOrEmpty(input)).ToReactiveCommand();
            TestCommand.Subscribe(async o => await Test());
        }

        public ReactiveProperty<string> Input { get; }
        public ReactiveProperty<bool> IsBusy { get; }
        public ReactiveCommand TestCommand { get; }

        private async Task Test()
        {
            IsBusy.Value = true;
            await Task.Delay(TimeSpan.FromSeconds(3));
            Messages.Add(Input.Value);
            Input.Value = "";
            IsBusy.Value = false;
        }
    }