TreeLib

This project provides a:

• .Net Standard Library (1.4, 1.6, 2.0) or a
• .Net framework 4.0 Library

with Generic methods to traverse k-ary trees in different orders (Post-Order, Pre-Order, Level-Order) of traversal. This implementation includes scalable algorithms that return IEnumerable<T> to make parsing large tree structures a piece of cake, as well, as Generic Exception handling to ensure that traversal algorithms complete despite unexpected errors on some nodes.

Review demo projects:

• in this solution,
• WPF FilterTreeView sample application, and read
• Advanced WPF TreeViews Part 3 of n
• Advanced WPF TreeViews Part 4 of n to learn more details.

Implementing something as complicated as a Post-Order traversal algorithm requires just:

• a project reference,
• a LINQ statement to find each set of children in the tree,
• and a simple for each loop to implement the operation on each tree node:

Console.WriteLine("(Depth First) PostOrder Tree Traversal V3");
items = TreeLib.Depthfirst.Traverse.PostOrder(root, i => i.Children);

foreach (var item in items)
{
  Console.WriteLine(item.GetPath());
}

This pattern leads to a clear-cut separation of:

• the traversal algorithm and
• the operations performed on each tree node (e.g.: Console.WriteLine(item.GetPath());).

The project in this repository contains a demo console project to demo its usage in more detail.

Supported Generic Traversal Methods

Breadth First

Level Order

See TreeLib.BreadthFirst.Traverse.LevelOrder implementation for:

• Trees with 1 root node (expects 1 <T> root item as parameter)
• Trees with multiple root nodes (expects an IEnumerable<T> root item as parameter)
• Generic Level-Order function and DemoDirectoryTreeTraversal

Depth First

PreOrder

See TreeLib.BreadthFirst.Traverse.PreOrder implementation for:

• Trees with 1 root node (expects 1 <T> root item as parameter)
• Trees with multiple root nodes (expects IEnumerable<T> root as parameter)
• Generic Pre-Order function and DemoDirectoryTreeTraversal

Postorder

See TreeLib.BreadthFirst.Traverse.Postorder implementation for:

• Trees with 1 root node (expects 1 <T> root item as parameter)
• Trees with multiple root nodes (expects IEnumerable<T> root item as parameter)
• Generic Post-Order function and DemoDirectoryTreeTraversal

Tip

• Read about Generic Tree and Linked List Traversal in C# to understand the usefulness of Generic traversal methods.

• Watch the Binary tree traversal: Preorder, Inorder, Postorder video to better understand what is what (and why these Traversal Order Names make some sense):

• Look into data structure books online Introduction to Trees, Binary Search Trees or offline Algorithms by Robert Sedgewick and Kevin Wayne, if you still need more background on tree structures