Treeviews

Treeviews are user interface controls and data-structure abstractions used to present hierarchical data in software applications. In data structure terms, a tree is a connected acyclic graph of nodes linked by parent-child relationships. A treeview shows a rooted tree, where every node has a single parent (except the root) and zero or more children. Each node typically contains a data payload and references to its children; many implementations also retain a reference to its parent. The depth of a node is its distance from the root, while the height of the tree is the maximum depth.

Core operations include inserting new nodes, removing nodes, and moving subtrees. Searching for a node usually relies on traversal. Common traversal orders are pre-order, in-order, post-order (used in different algorithms), and level-order (breadth-first). In user interfaces, treeviews support expanding and collapsing nodes, selecting nodes, and editing node labels; advanced features may include drag-and-drop rearrangement and lazy-loading of deeply nested branches.

Applications include file systems, where folders and files are shown as a hierarchical tree; organization charts, taxonomies, and software project explorers. The specific data structures and UI frameworks implement treeviews in various ways, from simple nested lists to specialized controls such as the Windows TreeView or web-based components that render trees with accessibility and keyboard navigation in mind.

Performance considerations arise with very large trees: techniques such as virtualization, lazy loading, and efficient update strategies can reduce rendering and memory usage. Overall, treeviews provide intuitive representations of hierarchical data and are widely used in both data structure design and graphical user interfaces.