Define UXML attributes for built-in types

To define UXML attributes for a custom control, add the UxmlAttribute attribute to the properties that you want to expose in UXML and UI Builder.

UxmlAttribute links fields or properties to UXML attributes. Unity automatically handles the conversion of values to and from UXML attribute strings as needed. Unity provides a set of built-in converters for common types, such as int, float, bool, string, and Vector2.

By default, UI Toolkit resolves the C# Camel case or Pascal case attribute names into lowercase words connected by hyphens. For example, a property named MyFloat or myFloat in C# becomes my-float in UXML and UI Builder. You can also customize the UXML attribute names.

The following example creates a custom control with multiple custom attributes:

using System;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UIElements;

[UxmlElement]
public partial class ExampleVisualElement : VisualElement
{
    [UxmlAttribute]
    public string myStringValue { get; set; }

    [UxmlAttribute]
    public int myIntValue { get; set; }

    [UxmlAttribute]
    public float myFloatValue { get; set; }

    [UxmlAttribute]
    public List<int> myListOfInts { get; set; }

    [UxmlAttribute, UxmlTypeReference(typeof(VisualElement))]
    public Type myType { get; set; }

    [UxmlAttribute]
    public Texture2D myTexture { get; set; }

    [UxmlAttribute]
    public Color myColor { get; set; }
}

The following example UXML document uses the custom control:

<ui:UXML xmlns:ui="UnityEngine.UIElements">
    <ExampleElement my-string-value="Hello World" my-int-value="123" />
    <ExampleElement my-float-value="3.14" my-list-of-ints="1,2,3" />
    <ExampleElement my-string-value="Hello World" my-int-value="123" />
    <ExampleElement my-texture="project://database/Assets/MyTexture.png" />
    <ExampleElement my-color="#FF0000FF" />
    <ExampleElement my-type="UnityEngine.UIElements.Button, UnityEngine.UIElementsModule" />
</ui:UXML>

Additional resources

• Define UXML attributes for complex data types