在Xamarin中，如何检查当前是否有DisplayAlert或DisplayActionSheet处于打开状态？

public class DialogHelper
{
    private static bool _isDialogOpen = false;

    public static void ShowAlert(string title, string message, Action callback)
    {
        _isDialogOpen = true;
        Device.BeginInvokeOnMainThread(() =>
        {
            Application.Current.MainPage.DisplayAlert(title, message, "OK", callback);
        });
    }

    public static void ShowActionSheet(string title, string cancel, params (string text, Action action)[] buttons)
    {
        _isDialogOpen = true;
        Device.BeginInvokeOnMainThread(() =>
        {
            Application.Current.MainPage.DisplayActionSheet(title, cancel, null, buttons.Select(b => b.text).ToArray(), (index) =>
            {
                buttons[index].action?.Invoke();
                _isDialogOpen = false;
            });
        });
    }

    public static bool IsDialogOpen()
    {
        return _isDialog::>```csharp
    public static bool IsDialogOpen()
    {
        return _isDialogOpen;
    }
}

public class DialogHelper
{
    public static event EventHandler DialogOpened;
    public static event EventHandler DialogClosed;

    public static void ShowAlert(string title, string message)
    {
        DialogOpened?.Invoke(null, EventArgs.Empty);
        Device.BeginInvokeOnMainThread(() =>
        {
            Application.Current.MainPage.DisplayAlert(title, message, "OK", () =>
            {
                DialogClosed?.Invoke(null, EventArgs.Empty);
            });
        });
    }

    public static void ShowActionSheet(string title, string cancel, params (string text, Action action)[] buttons)
    {
        DialogOpened?.Invoke(null, EventArgs.Empty);
        Device.BeginInvokeOnMainThread(() =>
        {
            Application.Current.MainPage.DisplayActionSheet(title, cancel, null, buttons.Select(b => b.text).ToArray(), (index) =>
            {
                buttons[index].action?.Invoke();
                DialogClosed?.Invoke(null, EventArgs.Empty);
            });
        });
    }
}

public class MainPageViewModel
{
    public MainPageViewModel()
    {
        DialogHelper.DialogOpened += DialogHelper_DialogOpened;
        DialogHelper.DialogClosed += DialogHelper_DialogClosed;
    }

    private bool _isDialogOpen = false;

    private void DialogHelper_DialogOpened(object sender, EventArgs e)
    {
        _isDialogOpen = true;
    }

    private void DialogHelper_DialogClosed(object sender, EventArgs e)
    {
        _isDialogOpen = false;
    }

    public bool IsDialogOpen()
    {
        return _isDialogOpen;
    }
}