/// <summary>
 /// Gets whether the given property is favourited
 /// </summary>
 public bool IsPropertyFavourited(Property property)
 {
     return Favourites.Any(p => p.Guid == property.Guid);
 }
        /// <summary>
        /// Toggles the favourited state of the given property.
        /// </summary>
        public void ToggleFavourite(Property property)
        {
            if (IsPropertyFavourited(property))
              {
            var matchingProperty = Favourites.Single(p => p.Guid == property.Guid);
            Favourites.Remove(matchingProperty);
              }
              else
              {
            Favourites.Add(property);
              }

              PersistState();
        }