Structure UI with C# scripts

Technical users can define the layout of the UI(User Interface) Allows a user to interact with your application. Unity currently supports three UI systems. More info
See in Glossary directly in C# scriptsA piece of code that allows you to create your own Components, trigger game events, modify Component properties over time and respond to user input in any way you like. More info
See in Glossary.

You can define the look of controls in a USS file, or modify the style properties of the control in your C# script.

Controls are interactive and represent a value that you can change. For example, a FloatField represents a float value. You can create C# scripts to change the value of a control, register a callback, or apply data binding.

Add controls to a UI with C# scripts

To use a control in a UI, add it to the visual treeAn object graph, made of lightweight nodes, that holds all the elements in a window or panel. It defines every UI you build with the UI Toolkit.
See in Glossary.

The following example adds a Button control to an existing visual tree.

var newButton = new Button("Click me!");
rootVisualElement.Add(newButton);

When adding controls to a UI hierarchy, the layout engine automatically handles the sizing and positioning. You can also override the size and position of visual elements.

Change the control value

To access or change the value of a control, use its value property.

The following example creates a Toggle control and a Button control. When you click the button, the value of the toggle flips.

// Create a toggle and register callback
m_MyToggle = new Toggle("Test Toggle") { name = "My Toggle" };
rootVisualElement.Add(m_MyToggle);

// Create button to flip the toggle's value
Button button01 = new Button() { text = "Toggle" };
button01.clicked += () =>
{
    m_MyToggle.value = !m_MyToggle.value;
};
rootVisualElement.Add(button01);

For more information about the properties of a specific control, see UI Toolkit built-in controls reference.

Register a callback

Controls that have value properties send an event if the value changes. You can register a callback to receive this event.

The following example creates a Toggle control and registers a callback:

// Create a toggle and register callback
m_MyToggle = new Toggle("Test Toggle") { name = "My Toggle" };
m_MyToggle.RegisterValueChangedCallback((evt) => { Debug.Log("Change Event received"); });
rootVisualElement.Add(m_MyToggle);

To learn more about callbacks and events, see Events Handling.

Apply data binding

You can bind controls to an object or a serialized property. For example, you can bind a FloatField control to a public float variable that belongs to a MonoBehaviour. When the control binds to the property, it automatically displays the value of the property. When you modify the control, the value of the property updates.

Similarly, when the property value changes through code, the UI displays the updated value. This two-way connection is useful when you create custom InspectorA Unity window that displays information about the currently selected GameObject, asset or project settings, allowing you to inspect and edit the values. More info
See in Glossary windows.

For more information about data binding, see SerializedObject data binding.

Not all controls are bindable. For a list of built-in controls and whether they support binding, see UI Toolkit built-in controls reference.

Additional resources

• Structure UI with UXML