enhetsregisteret

name	enhetsregisteret
description	Norwegian business registry (Brreg) client for looking up companies and organisations using AT.Common.Enhetsregisteret. Use this skill when looking up enheter or underenheter by organisation number, searching for companies, or fetching update history from the Norwegian Register of Business Enterprises.
license	MIT
metadata	{"domain":"backend","tags":"enhetsregisteret brreg norway business-registry organisation company dotnet client"}

Enhetsregisteret Skill — Arbeidstilsynet/dotnet-common

Arbeidstilsynet.Common.Enhetsregisteret (AT.Common.Enhetsregisteret.Publish) is a strongly-typed .NET client for the Norwegian Register of Business Enterprises (Brreg).

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Installation

dotnet add package Arbeidstilsynet.Common.Enhetsregisteret

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Dependency Injection Setup

using Arbeidstilsynet.Common.Enhetsregisteret.DependencyInjection;

builder.Services.AddEnhetsregisteret(
    builder.Environment,
    config =>
    {
        // Optional: override the Brreg API base URL
        // config.BrregApiBaseUrlOverwrite = "https://custom-url/";

        // Optional: disable in-memory caching
        // config.CacheOptions = new CacheOptions { Disabled = true };
    }
);

Automatic URL selection

Environment	API URL used
Production	https://data.brreg.no/
Non-production (dev, staging, …)	https://data.ppe.brreg.no/

Caching is enabled by default. Override with config.BrregApiBaseUrlOverwrite or disable with config.CacheOptions = new CacheOptions { Disabled = true }.

---

IEnhetsregisteret Interface

Inject IEnhetsregisteret into any service or controller.

public class MyService(IEnhetsregisteret enhetsregisteret) { }

Look up a single unit

// Main unit (enhet)
Enhet? enhet = await enhetsregisteret.GetEnhet("123456789");

// Sub-unit (underenhet)
Underenhet? underenhet = await enhetsregisteret.GetUnderenhet("987654321");

Both return null if the unit is not found or an error occurs.

Search

var searchParams = new SearchEnheterQuery
{
    Navn = "Arbeidstilsynet",
    Organisasjonsform = ["AS"],
};

var pagination = new Pagination { Page = 0, Size = 20 };

// Search main units
PaginationResult<Enhet>? enheter = await enhetsregisteret.SearchEnheter(searchParams, pagination);

// Search sub-units
PaginationResult<Underenhet>? underenheter = await enhetsregisteret.SearchUnderenheter(searchParams, pagination);

Returns null on error.

Update history

var query = new GetOppdateringerQuery
{
    Dato = DateTime.Today.AddDays(-7),
};

// Updates for main units
PaginationResult<Oppdatering>? enheterOps =
    await enhetsregisteret.GetOppdateringerEnheter(query, pagination);

// Updates for sub-units
PaginationResult<Oppdatering>? underenheterOps =
    await enhetsregisteret.GetOppdateringerUnderenheter(query, pagination);

---

Key Model Types

Type	Description
Enhet	Main business unit with name, organisation number, address, NACE codes, etc.
Underenhet	Sub-unit linked to a parent Enhet
Oppdatering	Record of a change to an Enhet or Underenhet
SearchEnheterQuery	Search filter: Navn, Organisasjonsnummer, OverordnetEnhetOrganisasjonsnummer, Organisasjonsform, StrictSearch, SortDirection, SortBy
GetOppdateringerQuery	Filter for update history: required DateTime Dato, long Oppdateringsid (default 1), string[] Organisasjonsnummer
Pagination	Page (page index) + Size (page size)
PaginationResult<T>	Elements, TotalElements, PageSize, PageIndex

---

Extension Methods

The EnhetsregisteretExtensions class (in Arbeidstilsynet.Common.Enhetsregisteret.Extensions) provides convenience methods on IEnhetsregisteret for common access patterns.

Batch lookups

// Get multiple enheter by org numbers
IEnumerable<Enhet> enheter = await enhetsregisteret.GetEnheter(["123456789", "987654321"]);

// Get multiple underenheter by org numbers
IEnumerable<Underenhet> underenheter = await enhetsregisteret.GetUnderenheter(["111111111", "222222222"]);

// Get all underenheter belonging to a hovedenhet
IEnumerable<Underenhet> children = await enhetsregisteret.GetUnderenheterByHovedenhet("123456789");

These methods handle pagination automatically and return all matching results.

IAsyncEnumerable overloads

For large result sets, extension overloads return IAsyncEnumerable<T> and stream pages lazily:

// Stream all matching enheter
await foreach (Enhet enhet in enhetsregisteret.SearchEnheter(new SearchEnheterQuery { Navn = "Arbeidstilsynet" }))
{
    // process each enhet as it arrives
}

// Stream all matching underenheter
await foreach (Underenhet ue in enhetsregisteret.SearchUnderenheter(new SearchEnheterQuery { Organisasjonsform = ["BEDR"] }))
{
    // ...
}

// Stream updates for enheter
await foreach (Oppdatering op in enhetsregisteret.GetOppdateringerEnheter(new GetOppdateringerQuery { Dato = DateTime.Today.AddDays(-7) }))
{
    // ...
}

// Stream updates for underenheter
await foreach (Oppdatering op in enhetsregisteret.GetOppdateringerUnderenheter(new GetOppdateringerQuery { Dato = DateTime.Today.AddDays(-7) }))
{
    // ...
}

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Notes

• All methods are async and return null for non-5xx failures (e.g. 404); 5xx responses cause an HttpRequestException to be rethrown.
• In-memory caching reduces repeated round-trips to Brreg for the same org number.
• For XML documentation on available search fields, see the source of SearchEnheterQuery.

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Adding Enhetsregisteret — Checklist

1. dotnet add package Arbeidstilsynet.Common.Enhetsregisteret
2. Register with services.AddEnhetsregisteret(environment)
3. Inject IEnhetsregisteret into your service
4. Handle null returns (not-found / error)
5. Use extension methods from EnhetsregisteretExtensions for batch lookups and streaming