public void AddElement(T element, TreeElement parent, int insertPosition)
{
if (element == null)
{
throw new ArgumentNullException("element", "element is null");
}
if (parent == null)
{
throw new ArgumentNullException("parent", "parent is null");
}
if (parent.children == null)
{
parent.children = new List <TreeElement>();
}
parent.children.Insert(insertPosition, element);
element.parent = parent;
TreeElementUtility.UpdateDepthValues(parent);
TreeElementUtility.TreeToList(m_Root, m_Data);
Changed();
}