Structure UI with C# scripts
Add and interact with UI controls in C#.
Read time 3 minutesLast updated 23 days ago
Technical users can define the layout of the UI directly in C# scripts.
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 represents a float value. You can create C# scripts to change the value of a control, register a callback, or apply data binding.
FloatFieldAdd controls to a UI with C# scripts
To use a control in a UI, add it to the visual tree.
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 property.
valueThe 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 callbackm_MyToggle = new Toggle("Test Toggle") { name = "My Toggle" };rootVisualElement.Add(m_MyToggle);// Create button to flip the toggle's valueButton 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 properties send an event if the value changes. You can register a callback to receive this event.
valueThe following example creates a Toggle control and registers a callback:
// Create a toggle and register callbackm_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 . 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.
MonoBehaviourSimilarly, when the property value changes through code, the UI displays the updated value. This two-way connection is useful when you create custom Inspector 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.
Access properties of a control's read-only children
Some controls have read-only child elements. For example, a control has a child. You can use UQuery to access the child's properties and override their values.
ListViewScrollViewThe following example changes the scroll speed of a control by overriding the property of the child:
ListViewmouseWheelScrollSizeScrollViewvar scrollView = listView.Q<ScrollView>();scrollView.mouseWheelScrollSize = 55;
Manage control states
Controls have different states that you can manage in your C# scripts. For example, you can enable or disable a control.
The following example creates a Toggle control and a Button control. When you click the button, the toggle is disabled.
// Create a toggle.Toggle myToggle = new Toggle("A Toggle");// Create a button to disable the toggle.Button button01 = new Button();button01.text = "Button01";button01.RegisterCallback<ClickEvent>(evt =>{ myToggle.SetEnabled(false);});
You can also implement a visual feedback change when the state changes in USS using the pseudo-classes. For example, to disable a toggle, use a selector that has the pseudo state:
disabled.unity-button:disabled{ background-color: #000000;}