Key Frame Collection. IList. Add(Object) 方法
virtual int System.Collections.IList.Add(System::Object ^ keyFrame) = System::Collections::IList::Add;
int IList.Add (object keyFrame);
Function Add (keyFrame As Object) As Integer Implements IList.Add
插入了新元素的位置，-1 指示该项未插入到集合中。The position into which the new element was inserted, or -1 to indicate that the item was not inserted into the collection.