# 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/apps/apps-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/apps/apps-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.
:::

## Using the Expression editor

To unlock the power of VB expressions in your app:

1. Create a new app.
2. Drag and drop controls in the app pages, or configure rules and events.
3. To edit the **General** properties of a control, or to configure an event rule, look for the "tune" icon ![docs image](https://dev-assets.cms.uipath.com/assets/images/apps/apps-image-280277-10751768.webp).
4. For the desired property, click **Open expression editor** and start writing your VB expressions.