PromptPlus

# PromptPlus ## **TreeMultiSelect<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 checks several nodes with tri-state checkboxes and confirms with Enter.

TreeMultiSelect<T> renders an arbitrary hierarchy of items of type T as a navigable tree with checkboxes. Containers show a tri-state box (unchecked / checked / indeterminate) that reflects the aggregate state of their descendants. You build the structure exactly like TreeSelect<T> — a required root, first-level nodes, and nested children — then the user checks nodes and confirms. Checking can cascade to descendants, be limited to leaves, or be constrained by a count range.

🔘 Only need to pick one node? Use the TreeSelect control — same tree model, single selection.

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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, cascade check, filtering, leaf-only, validation
Styles	The TreeMultiSelectStyles regions and how to recolor them

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When to use it

Use TreeMultiSelect<T> when…	Consider instead…
The data is hierarchical and the user checks several nodes	—
The user picks a single node	TreeSelect
The data is a flat multi-select list	MultiSelect
The data is tabular (multiple columns)	TableSelect

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Minimal example

using PromptPlusLibrary;

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

if (!result.IsAborted)
    foreach (var item in result.Content)
        PromptPlus.Console.WriteLine(item);

• TreeMultiSelect<string>("Check folders") 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 the array of checked values.

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Building the tree

You add nodes explicitly, exactly as in TreeSelect<T>. 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
    .TreeMultiSelect<string>("Check items")
    .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");

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 control sibling order.

A node with children renders as a container (with a tri-state checkbox); a node with none is a leaf.

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A richer example

using PromptPlusLibrary;

var tree = PromptPlus.Controls
    .TreeMultiSelect<Node>("Check services", "Space checks; Enter confirms")
    .Root(company)
    .TextSelector(n => n.Name)
    .ExtraInfo(n => n.Info)
    .CascadeCheck(true)                 // checking a container marks its descendants
    .CheckLeafOnly(false)              // containers can be checked too
    .Range(2, 4)                       // require between 2 and 4 checked items
    .Default([api, mobile])            // pre-check two nodes
    .DefaultMatchBy((a, b) => a.Id == b.Id);

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

This combines cascade checking, a count range, and pre-checked defaults — 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
Checking behavior	CheckLeafOnly, CascadeCheck, RecursiveMarkWithCtrlSpace, Range
Check rules	PredicateChecked, PredicateCheckedAsync
Initial values	Default, DefaultMatchBy
Read-only display	ViewOnly
Dynamic description	ChangeDescription, ChangeDescriptionAsync
History	EnableHistory
Appearance & behavior	Styles, Options
Run	Run

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Return value

TreeMultiSelect<T> returns ResultPrompt<T[]> — the array of checked node values.

Member	Meaning
.Content	The T[] of checked values (empty array if none)
.IsAborted	true when the user pressed Esc

var (nodes, aborted) = PromptPlus.Controls
    .TreeMultiSelect<string>("Folders")
    .Root("Company").TextSelector(n => n).DefaultMatchBy((a, b) => a == b)
    .Run();
if (!aborted) PromptPlus.Console.WriteLine($"{nodes.Length} checked");

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See also

• Methods — the full fluent API
• Operations — building the model, keyboard, cascade check, filtering, validation
• Styles — recolor the tree regions
• TreeSelect — single-choice sibling
• MultiSelect · TableSelect — flat and tabular pickers

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