/// <summary>
/// Gets the root node of a tree given a node in that tree.
/// </summary>
/// <typeparam name="T">The type of elements in the tree.</typeparam>
/// <param name="walker">
/// The <see cref="ITreeWalker<T>"/> that knows how to find the parent and child nodes.
/// </param>
/// <param name="node">
/// The node from which the search for the root node will begin.
/// </param>
/// <returns>
/// The root node of a tree.
/// </returns>
public static T GetRoot <T>(this ITreeWalker <T> walker, T node)
{
// Validate parameters.
if (walker == null)
{
throw new ArgumentNullException("walker");
}
if (node == null)
{
throw new ArgumentNullException("node");
}
// Get the node's ancestors and return the last one, or the node itself , if the node
// has no ancestors.
return
(walker
.GetAncestorsAndSelf(node)
.Last());
}
