#region my model

    [KnownType(typeof(model1))]
    [KnownType(typeof(model2))]
    [KnownType(typeof(model3))]
    public class TaskGroupObjects : List<IBaseObject>
    {
        #region sortFields
        class compare : IComparer<IBaseObject>
        {
            public int Compare(IBaseObjectfield1, IBaseObjectfield2)
            {
                return field1.Order - field2.Order;
            }
        }

        public void sortByOrder()
        {
            Sort(new compare());
        }
        #endregion
    }

public static bool HasProperty(this object your model, string propertyName)
{
    return obj.GetType().GetProperty(propertyName) != null;
}