# PageBody aboutToChange(RequestContext, PageBody)

This method is called before the service is invoked in change mode.

Input

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

Input/Output

- `PageBody` - This object contains the information that is to be submitted to the underlying service.

Return value

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

Throws

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

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

Parent topic: IChangeInterceptor Interface