# ListBox

> *Note*: You can check the Avalonia docs for the [ListBox](https://docs.avaloniaui.net/docs/controls/listbox) and [ListBox API](http://reference.avaloniaui.net/api/Avalonia.Controls/ListBox/) if you need more information.
>
> For Avalonia.FuncUI's DSL properties you can check [ListBox.fs](https://github.com/fsprojects/Avalonia.FuncUI/blob/master/src/Avalonia.FuncUI/DSL/ListBox.fs)

The list box is a multi-line control box for allowing a user to choose value.

### Usage

**Create a list box**

```fsharp
ListBox.create [
    ListBox.dataItems [ "Linux"; "Mac"; "Windows" ]
]
```

**Multiple Item Selection Mode**

You can choose different [ListBox Selection Modes](https://docs.avaloniaui.net/docs/controls/listbox#selectionmode). The default is to only select a single element.

```fsharp
ListBox.create [
    ListBox.dataItems [ "Linux"; "Mac"; "Windows" ]
    ListBox.selectionMode Selection.Multiple
]
```

**Using Discriminated Unions**

```fsharp
type OperatingSystem =
    | Linux
    | Mac
    | Windows

ListBox.create [
    ListBox.dataItems [ Linux; Mac; Windows ]
]
```

**Controlling Selected Item**

To override the controls default behavior you need to add both `selectedItem` and `onSelectedItemChanged`

```fsharp
ListBox.create [
    ListBox.dataItems [ "Linux"; "Mac"; "Windows" ]
    ListBox.selectedItem state.os
    ListBox.onSelectedItemChanged (fun os -> dispatch ChangeOs)
]
```

**Controlling Selected Item by Index**

To override the controls default behavior you need to add both `selectedItem` and `onSelectedItemChanged`

```fsharp
ListBox.create [
    ListBox.dataItems [ "Linux"; "Mac"; "Windows" ]
    ListBox.selectedIndex state.osIndex
    ListBox.onSelectedIndexChanged (fun os -> dispatch ChangeOsIndex)
]
```


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://funcui.avaloniaui.net/controls/listbox.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.