PromptPlus

# PromptPlus ## **TreeSelect<T>** [](https://www.nuget.org/packages/PromptPlus) [](https://opensource.org/licenses/MIT) [](https://dotnet.microsoft.com/)

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An expandable/collapsible hierarchy where the user browses nodes and picks one item, confirming with Enter.

TreeSelect<T> renders an arbitrary hierarchy of items of type T as a navigable tree. You build the structure explicitly — a required root, first-level nodes, and nested children — and the control decides at runtime whether each node is a container (has children) or a leaf. It expands and collapses branches lazily, filters against the full path, can restrict confirmation to leaves, and validates the choice before returning it.

☑️ Need to check several nodes at once? Use the TreeMultiSelect control — same tree model, with tri-state checkboxes.

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On this page

Sub-page	What you will find
Index (this page)	What it is, when to use it, first examples, the method map
Methods	Every fluent method — signature, parameters, defaults, and a snippet
Operations	Building the model, keyboard, expand/collapse, filtering, leaf-only, validation
Styles	The TreeSelectStyles regions and how to recolor them

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When to use it

Use TreeSelect<T> when…	Consider instead…
The data is hierarchical and the user picks one node	—
The user may check several nodes	TreeMultiSelect
The data is a flat list	Select
The data is tabular (multiple columns)	TableSelect
It is a yes/no or single-key answer	KeyPress / Confirm

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Minimal example

using PromptPlusLibrary;

var result = PromptPlus.Controls
    .TreeSelect<string>("Pick a folder")
    .Root("Company")                       // required
    .TextSelector(n => n)                  // required
    .DefaultMatchBy((a, b) => a == b)      // required
    .Run();

if (!result.IsAborted)
    PromptPlus.Console.WriteLine($"You chose {result.Content}");

• TreeSelect<string>("Pick a folder") creates a tree of strings. The type argument T is the node type.
• Root(...), TextSelector(...), and DefaultMatchBy(...) are required — see Operations → Building the tree model.
• .Run() renders the tree and blocks until Enter (confirm) or Esc (abort), returning a ResultPrompt<T?> whose Content is nullable.

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Building the tree

You add nodes explicitly. First-level nodes are children of the root; deeper nodes are added on the node objects returned to you:

using PromptPlusLibrary;

var tree = PromptPlus.Controls
    .TreeSelect<string>("Pick an item")
    .Root("Company")
    .TextSelector(n => n)
    .DefaultMatchBy((a, b) => a == b);

var eng     = tree.AddLast("Engineering");   // first-level → returns ITreeNode<string>
var backend = eng.AddLast("Backend");        // child of Engineering
backend.AddLast("API");                      // leaf
backend.AddLast("Database");                 // leaf
tree.AddLast("Sales");
tree.AddLast("HR");

var result = tree.Run();

• AddLast / AddFirst add a first-level node and return an ITreeNode<T> so you can attach children.
• Children are added the same way on the node: node.AddLast(...) / node.AddFirst(...).
• AddAfter / AddBefore insert a sibling relative to an existing node — handy for controlling order.

A node with children renders as a container (expandable); a node with none renders as a leaf.

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A richer example

using PromptPlusLibrary;

var tree = PromptPlus.Controls
    .TreeSelect<Node>("Pick a service", "Type to filter the full path")
    .Root(company)
    .TextSelector(n => n.Name)
    .ExtraInfo(n => n.Info)              // secondary text next to each node
    .PathSeparator('.')                 // Company.Engineering.Backend.API
    .ShowFullPath(true)                 // answer shows the full path
    .SelectLeafOnly()                   // only leaves can be confirmed
    .Filter(FilterMode.Contains)        // live filtering as the user types
    .DefaultMatchBy((a, b) => a.Id == b.Id);

BuildTree(tree);
var result = tree.Run();

This combines extra info, full-path display, leaf-only confirmation, and filtering — see Operations for how they behave together.

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Method map

Grouped by purpose. Full signatures and examples are on the Methods page.

Purpose	Methods
Build the tree	Root, AddLast, AddFirst, AddAfter, AddBefore
Populate from a source	Interaction, InteractionAsync
Node text & info	TextSelector, ExtraInfo, ExtraInfoAsync
Paths & paging	PathSeparator, ShowFullPath, PageSize
Filtering	Filter
Confirmation rules	SelectLeafOnly, PredicateSelected, PredicateSelectedAsync
Initial value	Default, DefaultMatchBy
Read-only display	ViewOnly
Dynamic description	ChangeDescription, ChangeDescriptionAsync
History	EnableHistory
Appearance & behavior	Styles, Options
Run	Run

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Return value

TreeSelect<T> returns ResultPrompt<T?> — the single chosen node value (nullable).

Member	Meaning
.Content	The selected T (or null/default only when aborted — ViewOnly with no Default still returns the root node)
.IsAborted	true when the user pressed Esc

var (node, aborted) = PromptPlus.Controls
    .TreeSelect<string>("Folder")
    .Root("Company").TextSelector(n => n).DefaultMatchBy((a, b) => a == b)
    .Run();
if (!aborted) PromptPlus.Console.WriteLine(node);

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See also

• Methods — the full fluent API
• Operations — building the model, keyboard, filtering, leaf-only, validation
• Styles — recolor the tree regions
• TreeMultiSelect — multiple-choice sibling
• Select · TableSelect — flat and tabular pickers

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