该函数会判断元素是否已经高亮显示了类名，并根据查找结果执行添加或删除。

This function then determines if the element already has the class name highlight, and removes or adds based on its findings.

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这个类也包括了允许你是否显示默认菜单的属性。

The class also includes properties that allow you to toggle between displaying and not displaying the default menu.

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获取或设置一个值，该值指示窗体区域是否由派生的邮件类显示。

Gets or sets a value that indicates whether the form region is displayed by derived message classes.

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