---
title: Implement and configure a computed field in your index
slug: '2320'
canonical_url: https://docs.coveo.com/en/2320/
collection: coveo-for-sitecore-v5
source_format: adoc
---
# Implement and configure a computed field in your index
Computed fields let you add entirely new fields in your [Coveo organization](https://docs.coveo.com/en/185/), in addition to the Sitecore template fields.

You can implement a computed field using the following steps:

## Step 1: Implement the computed field

. Create a new C# class library project called `Coveo.Custom`.
You'll need to reference the `Sitecore.ContentSearch` assembly.
. Create a new class that inherits from `Sitecore.ContentSearch.ComputedFields.IComputedIndexField`.

[source,c#]
```
 using System;
 using Sitecore;
 using Sitecore.ContentSearch;
 using Sitecore.ContentSearch.ComputedFields;
 
 namespace Coveo.Custom
 {
     public class MyComputedField : IComputedIndexField
     {
         /// <remarks>
         /// This property should be left empty. Instead, use the FieldName attribute in the configuration file to
         /// specify the name of the computed field.
         /// </remarks>
         public string FieldName { get; set; }
 
         /// <remarks>
         /// This property can optionally be used to specify the data type of the Sitecore field being currently processed. So instead of
         /// being automatically handled as a string (which is the default behavior), the field will be converted into the corresponding
         /// Coveo data type. If you leave the property as is, the value returned by ComputeFieldValue will be converted into
         /// a string automatically. Note that you can't specify the return type of the field in the configuration file.
         /// </remarks>
         public string ReturnType { get; set; }
 
         /// <remarks>
         /// This method is what actually determines the value of the computed field.
         /// </remarks>
         public object ComputeFieldValue(IIndexable p_Indexable)
         {
             // Returning null means that the field won't be created.
             // By default, any returned value is automatically converted into a string.
             return null;
         }
     }
 }
```

. Customize the class to meet your specific needs.

> **Important**
>
> * A computed field is processed for every Sitecore item that's re-indexed. To minimize the impact on the duration of the indexing process
> 
> ** Filter out items that your computed field shouldn't be added to.
> 
> ** Avoid doing HTTP requests.
> 
> ** Avoid querying a search index.
> 
> ** Ensure you optimize your code.
> 
> * Since computed field logic runs in the context of Sitecore, you can take advantage of using the Sitecore API.

> **Note**
>
> The `ReturnType` property should be set to the Sitecore data type of the value returned by the computed field.
> Ultimately, this value is converted to the corresponding Coveo data type.
> If you don't set any return type, the value is automatically converted to a string, and therefore be of type String in the Coveo index.
> Here are the supported Sitecore data types along with their corresponding Coveo data types.
> |===
> | Sitecore data type | Coveo index data type
> 
> | Integer
> | Integer
> 
> | Number
> | Floating point
> 
> | date
> | Date/time
> 
> | datetime  
>   
> (Ensure the `ComputeFieldValue` method returns the datetime value in `yyyy/MM/dd@HH:mm:ssZ` format.)
> | Date/time
> 
> | string
> | String
> |===

> **Note**
>
> To access the built-in fields of the item being processed by the computed field, cast the `IIndexable` parameter of the `ComputeFieldValue` method to `IIndexableBuiltinFields`.
> For example, do the following to access the template name:
> 
> [source,c#]
> ```
 public object ComputeFieldValue(IIndexable p_Indexable)
 {
     IIndexableBuiltinFields fields = (IIndexableBuiltinFields)p_Indexable;
     string templateName = fields.TemplateName;
     ...
 }
```

. Compile the project.
. Copy the `Coveo.Custom.dll` to the `bin` folder of your Sitecore instance (typically `<SITECORE_INSTANCE_ROOT>\bin` or `<SITECORE_INSTANCE_ROOT>\website\bin`).

## Step 2: Add the computed field in the configuration

. Open the `Coveo.SearchProvider.Custom.config` file in a text editor.
This file is typically located in `<SITECORE_INSTANCE_ROOT>\App_Config\Include\Coveo` or `<SITECORE_INSTANCE_ROOT>\website\App_Config\Include\Coveo`.

. Locate the `<fields hint="raw:AddComputedIndexField">` element.

```xml
<coveo>
  <defaultIndexConfiguration>
    <fieldMap>
      <fieldNames hint="raw:AddFieldByFieldName">
    </fieldMap>
        <documentOptions>
          <!--
            ...
          -->
          <fields hint="raw:AddComputedIndexField">
```


. Add a new `<field>` element as an immediate child of the `<fields hint="raw:AddComputedIndexField">` element.

```xml
 <field fieldName="mycoveofield">MyNamespace.ComputedFields.MyComputedField, MyNamespace.ComputedFields</field>
```
Replace the `fieldName` and XML element text values with the name you want for the Coveo index field, the proper full class name, and the assembly name.

> **Note**
>
> This configuration creates the computed field on indexing.

> **Important**
>
> Don't use special characters in computed field names.

. (Optional) Locate the `<fieldNames hint="raw:AddFieldByFieldName">` element.

```xml
<coveo>
  <defaultIndexConfiguration>
    <fieldMap>
      <fieldNames hint="raw:AddFieldByFieldName">
```

. (Optional) Add a new `<fieldType>` element as an immediate child of the `<fieldNames hint="raw:AddFieldByFieldName">` element.

```xml
<fieldType fieldName="mycoveofield" isSortable="true" isFacet="true" settingType="Coveo.Framework.Configuration.FieldConfiguration, Coveo.Framework" returnType="System.String"/>
```
Replace the `fieldName` attribute value with the name you chose earlier for your Coveo index field.
Replace the `returnType` attribute value with the [appropriate value](https://docs.coveo.com/en/2562#fieldnames) in the context.

> **Note**
>
> This configuration lets you specify special settings for the new field (for example, so that you may use the field as a facet or to sort search results).

## Step 3: Rebuild your search indexes

[Rebuild your search indexes](https://docs.coveo.com/en/2426#rebuilding-a-search-index-manually), or at least [re-index the Sitecore items which need the new field](https://docs.coveo.com/en/2426#re-indexing-a-section-of-your-content-tree-in-the-content-editor).

## Step 4: Validate the computed field has been added

Validate that your new field has been added on your items using the [**Content Browser**](https://platform.cloud.coveo.com/admin/#/orgid/content/browser/) ([platform-ca](https://platform-ca.cloud.coveo.com/admin/#/orgid/content/browser/) | [platform-eu](https://platform-eu.cloud.coveo.com/admin/#/orgid/content/browser/) | [platform-au](https://platform-au.cloud.coveo.com/admin/#/orgid/content/browser/)).

> **Warning**
>
> When running computed field code, check your logs for computed field errors indicating items aren't being indexed.
> Implement proper exception handling to avoid these issues.
> For example, you might want to stop the process or set a fallback value for a computed field when suitable.

## Step 5: Use your new field

Use the new field in whatever way is needed.
For example, you may want to [display it in a result template](https://docs.coveo.com/en/2834#adding-conditions-and-fields-to-a-result-template).