// Fills the object list with Tree nodes that are connected.
public void FillFromFile(string filename)
{
var lines = File.ReadLines(filename);
foreach (var line in lines)
{
string parent = line.Substring(0, 3);
string child = line.Substring(4, 3);
ObjectNode parentNode = GetObject(parent, true);
ObjectNode childNode = GetObject(child, true);
parentNode.AddChild(childNode);
childNode.SetParent(parentNode);
}
InitRoot(); // find the root by traversing upwards through the parents.
}