Comparing Model Item value with bool value

I am stuck at writing here what if condition is doing means If it finds a property of - this.ModelItem.Properties["IsGroupCalendar"] and it is of type System.Activities.Presentation.Model.ModelPropertyImpl. This is my code :

public List<FeatureParameter> getOperationParamters(Office365Model activityyModel, string op)
{
    List<FeatureParameter> _listparams = activityyModel.Features.Where(s => s.Name.Equals(op)).FirstOrDefault().Parameters;
    if (this.ModelItem.Properties["IsGroupCalendar"].Value == true)
    {
        List<FeatureParameter> Parametersleft = _listparams;
        int index = Parametersleft.FindIndex(x => x.ParamName.Equals("CalendarId"));
        Parametersleft.RemoveAt(index);
        return Parametersleft;
    }
    return _listparams;
}

enter image description here I need value to compared with bool value but how can I proceed