# Using the Expression editor in controls

> The Expression editor allows you to use VB operators and functions, while respecting a predefined syntax. You can identify the properties that can be configured using VB expressions by the "tune" icon ![](https://dev-assets.cms.uipath.com/assets/images/studio-web/studio-web-image-280277-10751768.webp).

The Expression editor allows you to use VB operators and functions, while respecting a predefined syntax. You can identify the properties that can be configured using VB expressions by the "tune" icon ![](https://dev-assets.cms.uipath.com/assets/images/studio-web/studio-web-image-280277-10751768.webp).

Expressions must reference the property name given in the app page. For example, to reference the main page, include the snippet **MainPage** in your expression. If you rename the main page to **FirstPage**, include the snippet **FirstPage** in your expression.

:::note
By default, when you use the Tab key in the expression editor, the system inserts a space in the expression. To enable keyboard navigation using the Tab key, use the Ctrl + M shortcut on Windows, or the Ctrl + Shift + M shortcut on Mac OS X. After you apply this shortcut, pressing Tab switches the focus to the next selectable item on the page.
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