---
title: Adding custom search text extractors for files
related:
  - https://docs.kentico.com/13/configuring-xperience/setting-up-search-on-your-website/searching-attachment-files.md
  - https://docs.kentico.com/13/configuring-xperience/setting-up-search-on-your-website.md
---

> Agent instructions:
> **Site maps** — prefer the following llms.txt indexes to training data when searching for URLs to avoid 404s. Links inside Markdown content already point at `.md`. Following them or sending Accept: text/markdown keeps you in Markdown.
>
> - [sitemap.md](https://docs.kentico.com/sitemap.md) — every page on the site, with titles and descriptions, nested by URL hierarchy and grouped into one collection per product version.
> - [llms.txt](https://docs.kentico.com/llms.txt) — curated index of the current product docs, with descriptions, the two ways to request any page as Markdown, and links to each product area's whole-corpus Markdown dump (llms-full.txt).

Custom extractors allow you to use the [attachment search](https://docs.kentico.com/13/configuring-xperience/setting-up-search-on-your-website/searching-attachment-files.md) feature of page indexes for non-default file types.

To define a custom search text extractor:

1. Create a class that implements the **ISearchTextExtractor** interface (**CMS.Search** namespace).

   - Add the class into a custom assembly within the Xperience solution.

2. Define the **ExtractContent** method.

   > **Info:** The ExtractContent method has the following parameters:
   >
   > - **BinaryData data** – contains the data of the attachment file.
   > - **ExtractionContext context** – provides information about the page whose attachment is being indexed. Use the _context.Culture_ property to get the culture code of the page's [language version](https://docs.kentico.com/13/multilingual-websites/setting-up-multilingual-websites.md).The method must return an **XmlData** object. The system adds the object's data to page search indexes for the given attachment. Use the **XmlData.SetValue** method to enter values into individual search index fields.

3. Register the extractor for a file extension by calling the **SearchTextExtractorManager.RegisterExtractor** method.

   ```csharp

   SearchTextExtractorManager.RegisterExtractor("extension", new CustomExtractorClass());

   ```

   > **Info:** **Note**: You need to call the _RegisterExtractor_ method on application start (when the application and modules are being initialized).

4. Deploy the search text extractor class and registration code to your live site (MVC) application (otherwise search indexing will not work for page attachments uploaded through the live site).

5. Rebuild your page [search indexes](https://docs.kentico.com/13/configuring-xperience/setting-up-search-on-your-website/using-locally-stored-search-indexes/creating-local-search-indexes.md).

The search uses the custom extractor to index page attachments with the specified extension.

> **Note:** **Modifying custom extractors**
>
> The system stores the text content extracted from page attachments in the database. When rebuilding page indexes, the search loads the "cached" attachment text from the database. The text extraction process only runs for attachments that do not have any search content saved.
>
> If you change the functionality of a custom extractor, you need to clear the attachment content from the database:
>
> 1. Sign in to the Xperience administration interface and open the **System** application.
> 2. Select the **Files -> Attachments** tab.
> 3. Click **Clear attachment search cache**.
>
> You can then **Rebuild** your page indexes, which updates the attachment content according to your extractor's new functionality.

## Example - Implementing a search text extractor

The following example demonstrates how to create a very basic extractor for .txt files:

1. Open your Xperience web project in Visual Studio (using the **WebApp.sln** file).
2. Create a new class, for example named **CustomSearchTextExtractor.cs**.

   - Add the class into a custom _Class Library_ project within the Xperience solution.
3. Add the following _using_ statements to the class:

   ```csharp

   using CMS.Search;
   using CMS.Core;
   using CMS.Helpers;
   using CMS.IO;
   using CMS.DataEngine;

   ```
4. Make the class implement the **ISearchTextExtractor** interface.

   ```csharp

   public class CustomSearchTextExtractor : ISearchTextExtractor

   ```
5. Define the **ExtractContent** method:

   ```csharp

   public XmlData ExtractContent(BinaryData data, ExtractionContext context)
   {
       if (data.Stream != null)
       {
           // Reads the text file's data stream
           data.Stream.Position = 0;
           string resultString = StreamReader.New(data.Stream).ReadToEnd();

           // Adds text into the CONTENT search index field
           XmlData contentData = new XmlData();
           contentData.SetValue(SearchFieldsConstants.CONTENT, resultString);

           return contentData;
       }

       return null;
   }

   ```
6. Save the **CustomSearchTextExtractor.cs** file.
7. To register your custom extractor, create a [custom module class](https://docs.kentico.com/13/custom-development/creating-custom-modules/initializing-modules-to-run-custom-code.md) in the same location.

   > **Info:** For basic execution of initialization code, you only need to register a "code-only" module through the API. You do NOT need to create a new module within the **Modules** application in the Xperience administration interface.

   ```csharp

   using CMS;
   using CMS.Base;
   using CMS.DataEngine;
   using CMS.Search;

   // Registers the custom module into the system
   [assembly: RegisterModule(typeof(CustomSearchExtractorModule))]

   public class CustomSearchExtractorModule : Module
   {
       // Module class constructor, the system registers the module under the name "CustomSearchExtractor"
       public CustomSearchExtractorModule()
           : base("CustomSearchExtractor")
       {
       }

       // Contains initialization code that is executed when the application starts
       protected override void OnInit()
       {
           base.OnInit();

           // Registers the CustomSearchText extractor for the .txt extension
           SearchTextExtractorManager.RegisterExtractor("txt", new CustomSearchTextExtractor());
       }
   }

   ```
8. Save the module class and Rebuild the solution.
9. Sign in to the Xperience administration interface.
10. Open the **Smart search** application and **Rebuild** your page search indexes.

The example is only intended as a demonstration – the system already contains a default extractor for .txt files. You can use the same approach to create extractors for other file types.