How to Get and Set Lookup Fields in Dynamics 365 CRM (JavaScript, Power Automate, Plugins, Web API)

In this blog, we’ll cover how to work with lookups in four ways:

• JavaScript (form scripts)

• Power Automate (Flow)

• Plugins (C#)

• Web API (OData / REST API)

Finally, we’ll walk through real-world examples you can apply directly in your projects.

🔹 1. Handling Lookups with JavaScript in Dynamics 365 CRM

Form scripts are useful when you want to manipulate lookup fields directly on CRM forms.

✅ Get a Lookup Value in JavaScript

function getLookupValue(executionContext) {
    var formContext = executionContext.getFormContext();
    var lookup = formContext.getAttribute("parentaccountid").getValue();

    if (lookup != null) {
        var id = lookup[0].id;       // GUID of the record
        var name = lookup[0].name;   // Display name
        var entity = lookup[0].entityType; // Entity logical name

        console.log("ID: " + id + " | Name: " + name + " | Entity: " + entity);
    }
}

✅ Set a Lookup Value in JavaScript

function setLookupValue(executionContext) {
    var formContext = executionContext.getFormContext();

    var lookupValue = [{
        id: "B0D4F3F4-1D3A-4D2A-9A54-8A1B2E6A9F6C",
        name: "Contoso Ltd",
        entityType: "account"
    }];

    formContext.getAttribute("parentaccountid").setValue(lookupValue);
}

🔹 2. Handling Lookups in Power Automate (Flow)

In Power Automate, lookup fields need to be set using the @odata.bind notation.

✅ Get a Lookup Value in Flow

When retrieving a Contact, a lookup field looks like this:

"_parentaccountid_value": "b0d4f3f4-1d3a-4d2a-9a54-8a1b2e6a9f6c"

✅ Set a Lookup Value in Flow

To set a lookup, use:

"parentaccountid@odata.bind": "/accounts(b0d4f3f4-1d3a-4d2a-9a54-8a1b2e6a9f6c)"

💡 In Flow expressions, you can build it dynamically:

concat('/accounts(', outputs('Get_Account')?['body/accountid'], ')')

🔹 3. Handling Lookups in Plugins (C#)

In Dynamics 365 Plugins, lookups are handled using the EntityReference class.

✅ Get a Lookup Value in Plugin

if (entity.Contains("parentaccountid") && entity["parentaccountid"] is EntityReference lookup)
{
    Guid id = lookup.Id;
    string name = lookup.Name;       // Sometimes null depending on context
    string logicalName = lookup.LogicalName;
}

✅ Set a Lookup Value in Plugin

entity["parentaccountid"] = new EntityReference("account", 
    new Guid("B0D4F3F4-1D3A-4D2A-9A54-8A1B2E6A9F6C"));

🔹 4. Handling Lookups in Dynamics 365 Web API

When working with the Dataverse Web API, lookup values are accessed using the _fieldname_value convention.

✅ Get a Lookup Value via Web API

GET [Organization URI]/api/data/v9.2/contacts(11111111-2222-3333-4444-555555555555)?$select=fullname,_parentcustomerid_value

Response:

{
  "fullname": "John Doe",
  "_parentcustomerid_value": "b0d4f3f4-1d3a-4d2a-9a54-8a1b2e6a9f6c",
  "_parentcustomerid_value@OData.Community.Display.V1.FormattedValue": "Contoso Ltd",
  "_parentcustomerid_value@Microsoft.Dynamics.CRM.lookuplogicalname": "account"
}

• _parentcustomerid_value → The GUID of the lookup

• FormattedValue → The display name

• lookuplogicalname → The entity type

✅ Set a Lookup Value via Web API

PATCH [Organization URI]/api/data/v9.2/contacts(11111111-2222-3333-4444-555555555555)
Content-Type: application/json

{
  "parentcustomerid_account@odata.bind": "/accounts(b0d4f3f4-1d3a-4d2a-9a54-8a1b2e6a9f6c)"
}

🔹 Real-World Examples

Let’s look at some common business scenarios where you’ll need to get or set lookup fields.

Example 1: Setting a Contact’s Parent Account (JavaScript)

When a user selects an Industry, automatically assign the Contact to a default Account:

if (formContext.getAttribute("industrycode").getValue() === 42) {
    var accountLookup = [{
        id: "D1C5E8F2-91AA-4C3E-8A14-7C32F1B9F77B",
        name: "Default Industry Account",
        entityType: "account"
    }];
    formContext.getAttribute("parentaccountid").setValue(accountLookup);
}

Example 2: Assigning a Record Owner in Power Automate

When a new Lead is created, assign it to a specific user:

"ownerid@odata.bind": "/systemusers(5a4b8f3f-1122-44aa-bbbb-998877665544)"

Example 3: Updating Related Account from a Plugin

If a Contact is marked as "VIP", set its Parent Account to “VIP Clients”:

if (entity.Contains("new_vipstatus") && (bool)entity["new_vipstatus"] == true)
{
    entity["parentaccountid"] = new EntityReference("account", 
        new Guid("E2F6B8D1-99F1-4B4D-8CC9-11B2A3D3F1AA"));
}

Example 4: Web API — Linking a Case to a Customer

PATCH [Organization URI]/api/data/v9.2/incidents(11111111-2222-3333-4444-555555555555)
Content-Type: application/json

{
  "customerid_contact@odata.bind": "/contacts(b0d4f3f4-1d3a-4d2a-9a54-8a1b2e6a9f6c)"
}

🎯 Conclusion

• JavaScript → Use getValue() and setValue() with {id, name, entityType} objects.

• Power Automate (Flow) → Use @odata.bind with /entityname(guid) syntax.

• Plugins (C#) → Work with EntityReference.

• Web API → Use _lookupfield_value for retrieval and @odata.bind for updates.

Understanding how to get and set lookups across different technologies in Dynamics 365 CRM makes your solutions more flexible, scalable, and maintainable.