Creating a XML List for TXB

Hi guys,

I'm trying to create a list that is passed to TXB using this code taken from the XML deserializer section:

// A generic, "contains anything", list:
      public List<object> SceneData;
      // An array of floats (borrowed from T2DAnimationComponent.Animation):
      public float[] CurveRange
      {
        get { return _curveRange; }
        set { _curveRange = value; _curveDirty = true; }
      }
      // A special "XML property" list (see below for an explanation):
      [TorqueXmlDeserializeInclude]
      [XmlElement(ElementName = "Forces")]
      internal List<Force> _XMLForces
      {
        get { return null; }
        set
        {
          for (int i = 0; i < value.Count; i++)
          {
            AddForce(value[i]);
          }
        }
      }

But when i try to import it, the complier dosn't like " [XmlElement" what is wrong?? Is it says its missing a reference or assembly but im not quite sure if i am actually missing one.

Thanks in advance.