Dynamics 365 Business Central: Does the API support Multi-level Expand (Multi layers)

Hi, Readers.
Today I would like to discuss a question I was asked recently, does the BC API support Multi-level Expand?

With Business Central you can create Connect apps. Connect apps establish a point-to-point connection between Dynamics 365 Business Central and a 3rd party solution or service and is typically created using standard REST API to interchange data. More details: Welcome to the API (v2.0) for Business Central
For example, salesOrder resource type (standard API): Represents a sales order in Business Central.
Endpoint:

https://api.businesscentral.dynamics.com/v2.0/c8558e71-6ad8-4fcd-9f29-3ca165b41bbe/Sandbox240/api/v2.0/companies(37052e92-60e6-ee11-a200-6045bdac9711)/salesOrders

In this standard API, we can use some navigation, which can expand the next layer of data.
Navigation:

Navigation	Return Type	Description
customer	customer	Gets the customer of the salesOrder.
dimensionValue	dimensionValue	Gets the dimensionvalue of the salesOrder.
currency	currency	Gets the currency of the salesOrder.
paymentTerm	paymentTerm	Gets the paymentterm of the salesOrder.
shipmentMethod	shipmentMethod	Gets the shipmentmethod of the salesOrder.
dimensionSetLines	dimensionSetLines	Gets the dimensionsetlines of the salesOrder.
salesOrderLines	salesOrderLines	Gets the salesorderlines of the salesOrder.
attachments	attachments	Gets the attachments of the salesOrder.
documentAttachments	documentAttachments	Gets the documentattachments of the salesOrder.

$expand: Retrieves related resources.

Let’s see two examples.
customer:

https://api.businesscentral.dynamics.com/v2.0/c8558e71-6ad8-4fcd-9f29-3ca165b41bbe/Sandbox240/api/v2.0/companies(37052e92-60e6-ee11-a200-6045bdac9711)/salesOrders?$expand=customer

salesOrderLines:

https://api.businesscentral.dynamics.com/v2.0/c8558e71-6ad8-4fcd-9f29-3ca165b41bbe/Sandbox240/api/v2.0/companies(37052e92-60e6-ee11-a200-6045bdac9711)/salesOrders?$expand=salesOrderLines

The examples above are all single-level (layer). Does the BC API support Multi-level (Multi layers)? Yes, of course. Let’s take a look at a few more examples.

salesOrders -> salesOrderLines -> item:

https://api.businesscentral.dynamics.com/v2.0/7e47da45-7f7d-448a-bd3d-1f4aa2ec8f62/Sandbox273/api/v2.0/companies(0b675e81-5ef3-f011-8405-000d3a524295)/salesOrders?$expand=salesOrderLines($expand=item)

salesOrders -> salesOrderLines -> item -> itemCategory:

https://api.businesscentral.dynamics.com/v2.0/7e47da45-7f7d-448a-bd3d-1f4aa2ec8f62/Sandbox273/api/v2.0/companies(0b675e81-5ef3-f011-8405-000d3a524295)/salesOrders?$expand=salesOrderLines($expand=item($expand=itemCategory))

Therefore, each additional level of expansion requires an extra set of parentheses: $expand=salesOrderLines($expand=item($expand=itemCategory))

You can also expand multiple entities simultaneously, such as combining a two-level expand with a multi-level (three-level) nested expand.

https://api.businesscentral.dynamics.com/v2.0/7e47da45-7f7d-448a-bd3d-1f4aa2ec8f62/Sandbox273/api/v2.0/companies(0b675e81-5ef3-f011-8405-000d3a524295)/salesOrders?$expand=paymentTerm,salesOrderLines($expand=account,item($expand=itemCategory))

This also allows you to add filter expressions. More details: Dynamics 365 Business Central: How to use filter expressions in API related resource ($expand)

https://api.businesscentral.dynamics.com/v2.0/7e47da45-7f7d-448a-bd3d-1f4aa2ec8f62/Sandbox273/api/v2.0/companies(0b675e81-5ef3-f011-8405-000d3a524295)/salesOrders?$filter=orderDate ge 2026-01-01&$expand=paymentTerm,salesOrderLines($expand=account,item($expand=itemCategory))

And although the syntax becomes more complex, you can also include a **$select** clause at each level to retrieve only the necessary fields.

https://api.businesscentral.dynamics.com/v2.0/7e47da45-7f7d-448a-bd3d-1f4aa2ec8f62/Sandbox273/api/v2.0/companies(0b675e81-5ef3-f011-8405-000d3a524295)/salesOrders?$select=number,postingDate&$expand=paymentTerm($select=code,displayName),salesOrderLines($select=lineObjectNumber;$expand=account,item($select=displayName;$expand=itemCategory))

Great. Give it a try!!!😁

PS: Dynamics 365 Business Central Blog Series: REST API web services (APIs)

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Hope this will help.

Thanks for reading.

ZHU