如何获得XAML命令执行异步

假设我有以下命令

public class SignOutCommand : CommandBase, ISignOutCommand
{
    private readonly UserModel _userModel;
    private readonly IUserService _userService;
    public SignOutCommand(IUserService userService)
    {
        _userService = userService;
        _userModel = App.CurrentUser;
    }
    public bool CanExecute(object parameter)
    {
        var vm = parameter as EditProfileViewModel;
        return vm != null;
    }
    public Task<bool> CanExecuteAsync(object parameter)
    {
        return Task.Run(() => CanExecute(parameter);
    }
    public void Execute(object parameter)
    {
        var vm = (EditProfileViewModel)parameter;
        var signOutSucceeded = SignOutUser();
        if (signOutSucceeded)
        {
            vm.AfterSuccessfulSignOut();
        }
    }
    public Task ExecuteAsync(object parameter)
    {
        return Task.Run(() => Execute(parameter);
    }
    private bool SignOutUser()
    {
        // populate this so that we get the attached collections.
        var user = _userService.GetByEmailAddress(_userModel.Email);
        _userService.RevokeLoggedInUser(user);
        return true;
    }
}

我的XAML有一个按钮

        <Button Text="Sign out"
                Command="{Binding SignOutCommand}"
                CommandParameter="{Binding}" />

执行ExecuteAsync而不是Execute需要什么?对不起，如果这是微不足道的，我对XAML相当陌生。

同样，我实际上在Xamarin中做这个。Forms XAML，不确定这里是否有区别

public class SignOutCommand : ICommand
{
    public bool CanExecute(object parameter)
    {
        var vm = parameter as EditProfileViewModel;
        return vm != null;
    }
    public async void Execute(object parameter)
    {
        Task.Run(() => 
        {
            var vm = (EditProfileViewModel)parameter;
            var signOutSucceeded = SignOutUser();
            if (signOutSucceeded)
            {
                vm.AfterSuccessfulSignOut();
            }
        }
    }
    ...
}