# PageBody aboutToAdd(RequestContext, PageBody)

This method is called before the service is invoked.

Input

- `RequestContext` - Contains session parameters, such as language cd, user id, and so on.

Input/Output

- `PageBody` - The input page body to be added.

Return value

- `PageBody or null` - If a page body is returned, this is considered the result of the service and the underlying service will not be executed. If null is returned, the service will run normally.

Throws

`InterceptorError` - Throw this exception when an error occurs.

`InterceptorWarning` - Throw this exception to signal an application warning.

Parent topic: IAddInterceptor Interface