You can write to style to set style values to an element. However, to get the final computed styles of an element, read from resolvedStyle.
In a C# script, you can set styles directly to the style properties of a visual element. For example, the following code sets the background color of a button to red:
button.style.backgroundColor = Color.red
You can also add a Unity style sheet (USS) to any visual element. Unity represents USS files as StyleSheet objects in C# scripts.
To add style sheets to a visual element:
StyleSheet objects with standard Unity APIs, such as AssetDatabase.Load() or Resources.Load().styleSheets property of a visual element to add the StyleSheet object.For example, given a style sheet in the local variable styleSheet and an element in the local variable element, the following example adds the style sheet to the element:
element.styleSheets.Add(styleSheet);
Note: Style rules apply to the visual element and all its descendants, but don’t apply to the parent or siblings of the element. Any change to the USS file automatically refreshes the UI that uses this style sheet.
Style values on an element are computed from various sources, including multiple applied classes, inheritance from ancestors, and inline styles from UXML or C# code. These values might change from frame to frame. The style only holds the inline styles for the element and does not reflect other sources. The resolvedStyle has the final calculated values, considering all sources on the current frame.
For example, when you use the inline style to set the width for an element, both the style and resolvedStyle start with the same value. When the element is added to the hierarchy, resolvedStyle.width could be NaN until the layout updates. If you define the width in a class as a percentage, the computed width relies on parent properties such as border-width and padding. Although style.width might give a relative value, such as for transitions that can change value, resolvedStyle.width gives the actual rendered width.
The following example shows how to get the final computed width of an element:
float width = element.resolvedStyle.width;