> For the complete documentation index, see [llms.txt](https://docs.flatredball.com/gum/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.flatredball.com/gum/code/controls/scrollbar.md).

# ScrollBar

## Introduction

ScrollBar is a Forms control that lets the user select a numeric value by interacting with a draggable thumb, up/down buttons, and a track. It is most commonly used internally by [ScrollViewer](/gum/code/controls/scrollviewer.md), which creates and manages a ScrollBar automatically. Use ScrollBar directly when you need a standalone scrollbar that is not tied to a ScrollViewer — for example, to control a custom camera offset or to expose a scrollable range in a data-driven panel.

If you want a scrollable container that manages content layout for you, use [ScrollViewer](/gum/code/controls/scrollviewer.md) instead.

<figure><img src="/files/wE59wpWzVRnSUrx7HARw" alt=""><figcaption><p>ScrollBar control</p></figcaption></figure>

## Key Properties

* **`Value`** — The current numeric value. Always clamped between `Minimum` and `Maximum`. Set this in code to scroll the bar programmatically.
* **`Minimum`** — The lower bound of the range (inclusive). Defaults to `0`.
* **`Maximum`** — The upper bound of the range (inclusive). Defaults to `100`.
* **`SmallChange`** — The amount `Value` changes when the user clicks the up or down arrow buttons, or scrolls the mouse wheel over the scrollbar.
* **`LargeChange`** — The amount `Value` changes when the user clicks on the track (the area between the thumb and the arrow buttons).

## Events

* **`ValueChanged`** — Raised whenever `Value` changes, regardless of whether the change came from the UI or from code.
* **`ValueChangeCompleted`** — Raised when a discrete value change finishes (e.g. after releasing the thumb or clicking an arrow button). Use this to avoid reacting every frame during a drag.

## Code Example: Creating a Standalone ScrollBar

The following code creates a vertical ScrollBar, configures its range and change amounts, and subscribes to `ValueChanged` to react whenever the value is updated.

```csharp
// Initialize
var label = new Label();
label.AddToRoot();
label.X = 50;
label.Y = 20;

var scrollBar = new ScrollBar();
scrollBar.AddToRoot();
scrollBar.X = 50;
scrollBar.Y = 50;
scrollBar.Width = 24;
scrollBar.Height = 200;
scrollBar.Minimum = 0;
scrollBar.Maximum = 100;
scrollBar.SmallChange = 5;
scrollBar.LargeChange = 20;
scrollBar.Value = 0;
scrollBar.ValueChanged += (_, _) =>
    label.Text = $"ScrollBar value: {scrollBar.Value}";
```

[Try on XnaFiddle.NET](https://xnafiddle.net/#snippet=H4sIAAAAAAAAA2WQQQvCMAyF_0ooHhRE5tTLZAcVUUEvKupAkOrCVug2mK2K4n-37bS6eev78vLS5EFm54lMiCdyiU3CUiYY5eyOxCMXmgOnR-TgQ4pXmOt3vdHfp4a2BmG4zpZZJn7YTnl7jpWBkq6WOut8yjPOh-pV5K0-2vTbaiX3y232FwX_aMtCEeux3RKeIotiYb5T9i_UzolMVKXC6e3N25WOVUI5H8U0jVCPL9XmNI_Q1txy44ZyiX-DDC1aQthLx3GHPtQPTTg0wNe6M_6cc403vULNuFx7P7joCA8eldBn4euT5wuoARPg5wEAAA)

## ScrollBar and ScrollViewer

In most cases you do not need to create a ScrollBar directly. [ScrollViewer](/gum/code/controls/scrollviewer.md) instantiates and manages one internally, and exposes `VerticalScrollBarValue` to read or set the scroll position in code. Use a standalone ScrollBar only when you need fine-grained control over a scrollable range that is not tied to a ScrollViewer's content panel.


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## 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, and the optional `goal` query parameter:

```
GET https://docs.flatredball.com/gum/code/controls/scrollbar.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

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.