<Button IsEnabled="{Binding CanDo}"
        Command="{Binding AsyncTest}"/>
<Button Command="{Binding CancelTest, UpdateSourceTrigger=PropertyChanged}"/>

        public bool CanDo
        {
            get => _canDo;
            set
            {
                if (Set(ref _canDo, value)) CancelTest.RaiseCanExecuteChanged();
            }
        }
//в конструкторе:
            CancellationTokenSource cancellationTokenSource = new ();
//Асинхронная команда
            AsyncTest = new AsyncCommand(AsyncTestDo, cancellationTokenSource, errorCancelHandler: _errorCancelHandler);
//Обычная команда
            CancelTest = new Command(
                () => AsyncTest.Cancel(), 
                () => !CanDo && !cancellationTokenSource.IsCancellationRequested, 
                _errorCancelHandler);


        private async Task AsyncTestDo(CancellationToken? c)
        {
            try
            {
                CanDo = false;
		while (true)
                {
                    if (c?.IsCancellationRequested ?? false)
                    {
                        throw new OperationCanceledException("Отменили эту бодягу))))");
                    }
//тут что-то делаем
		}
            }
            finally
            {
                CanDo = true;
                AsyncTest?.ResetCancel();
            }
        }