public void WhenOpenDialogsAreOpenIsExist()
{
object id = Guid.NewGuid();
_dialogHost.Identifier = id;
bool isExist = false;
_ = _dialogHost.ShowDialog("Content", new DialogOpenedEventHandler((sender, arg) =>
{
isExist = DialogHost.IsExistDialog(id);
}));
Assert.True(isExist);
DialogHost.CloseDialogCommand.Execute(null, _dialogHost);
Assert.False(DialogHost.IsExistDialog(id));
}