private IEnumerable <BinaryTree <T> > OutOrderTraverse()
{
if (RightNode != null)
{
foreach (var item in RightNode.OutOrderTraverse())
{
yield return(item);
}
}
yield return(this);
if (LeftNode != null)
{
foreach (var item in LeftNode.OutOrderTraverse())
{
yield return(item);
}
}
}