# Sandbox.UI.MixinDefinition

Represents a parsed @mixin definition that can be included elsewhere.

- Kind: class
- Namespace: `Sandbox.UI`
- Assembly: `Sandbox.Engine`
- Modifiers: sealed

## Constructors

- [`MixinDefinition`](/api/Sandbox.UI.MixinDefinition/.ctor)

## Properties

- [`Content`](/api/Sandbox.UI.MixinDefinition/Content): The raw content of the mixin body, to be expanded when included. This includes nested rules which will be parsed during expansion.
- [`FileLine`](/api/Sandbox.UI.MixinDefinition/FileLine): Source line for error messages
- [`FileName`](/api/Sandbox.UI.MixinDefinition/FileName): Source file for error messages
- [`HasVariadicParameter`](/api/Sandbox.UI.MixinDefinition/HasVariadicParameter): Whether this mixin has a variadic parameter (last param ends with ...)
- [`Name`](/api/Sandbox.UI.MixinDefinition/Name): The name of the mixin (e.g., "button" from "@mixin button")
- [`Parameters`](/api/Sandbox.UI.MixinDefinition/Parameters): Parameter definitions in order, with optional default values. Key = parameter name (without $), Value = default value (null if required)

## Methods

- [`Expand`](/api/Sandbox.UI.MixinDefinition/Expand)