How to include custom properties in examine search result of Umbraco

How to include custom properties in examine search result of Umbraco

Environment
- Umbraco version 7.6.3 assembly: 1.0.6361.21154
- VS2015




1. Add new properties "Exclude From Search" in backoffice

2. Add the custom properties in ExamineIndex.config

  <IndexSet SetName="PDFIndexSet" IndexPath="~/App_Data/TEMP/ExamineIndexes/PDFs">
    <IndexAttributeFields>

    </IndexAttributeFields>
    <IndexUserFields>
      <add Name="excludeFromSearch"/>
    </IndexUserFields>
  </IndexSet>