The .NET SDK (econnect-psb-dotnet) is the official C# client for the PSB REST API. The NuGet package EConnect.Psb provides typed interfaces for all API groups and supports dependency injection in ASP.NET Core.

• .NET Core 2.0 or higher, or .NET Framework 4.6.1+

Via the .NET CLI:

dotnet add package EConnect.Psb

Via Package Manager Console:

Install-Package EConnect.Psb

For webhook validation in ASP.NET Core MVC:

dotnet add package EConnect.Psb.AspNetCore.Mvc

The recommended setup uses AddPsbService in your Program.cs or Startup.cs:

builder.Services.AddPsbService(options =>
{
    options.Username = "your-username";           // for Resource Owner flow
    options.Password = "your-password";           // for Resource Owner flow
    options.PsbUrl = "https://accp-psb.econnect.eu";
    options.IdentityUrl = "https://accp-identity.econnect.eu";
    options.ClientId = "your-client-id";
    options.ClientSecret = "your-client-secret";
    options.SubscriptionKey = "your-subscription-key"; // optional, legacy
});

Which OAuth2 flow you use determines which fields you fill in. See Authentication for Client Credentials versus Resource Owner Password Credentials.

After registration you can inject the following interfaces:

Example in a controller:

public class InvoiceController
{
    private readonly IPsbSalesInvoiceApi _salesInvoice;

    public InvoiceController(IPsbSalesInvoiceApi salesInvoice)
    {
        _salesInvoice = salesInvoice;
    }
}

All interfaces are public and therefore mockable in unit tests.

The repository includes a working example in EConnect.Psb.Web.Example:

• ExampleSendInvoice.cshtml.cs — upload an invoice via Peppol

The pattern follows the SalesInvoice endpoint: upload an XML document; the PSB validates and routes automatically.

If dependency injection is not available, use PsbServiceHost:

using var psb = PsbServiceHost.Create(options =>
{
    options.Username = "your-username";
    options.Password = "your-password";
    options.PsbUrl = "https://accp-psb.econnect.eu";
    options.IdentityUrl = "https://accp-identity.econnect.eu";
    options.ClientId = "your-client-id";
    options.ClientSecret = "your-client-secret";
    options.SubscriptionKey = "your-subscription-key";
});

var result = await psb.SalesInvoice
    .QueryRecipientParty("{senderPartyId}", new[] { "{receiverPartyId}" })
    .ConfigureAwait(false);

Console.WriteLine(result);

A console example is available in EConnect.Psb.ConsoleNet.Example.

PSB webhooks are secured with the X-EConnect-Signature header. The EConnect.Psb.AspNetCore.Mvc package validates that signature via an attribute on your controller method.

Hardcoded secret:

[PsbWebhook("mySecret")]
public IActionResult Webhook([PsbWebhookValidSentOn] PsbWebHookEvent @event)
{
    // process webhook event
    return Ok();
}

Secret from configuration:

[PsbWebhookOptions("webhook")]
public IActionResult Webhook([PsbWebhookValidSentOn] PsbWebHookEvent @event)
{
    return Ok();
}

More about webhook configuration: Configure webhooks.

The SDK throws exceptions on HTTP errors. In production, implement:

• 401 — token expired; the service usually re-authenticates automatically on the next call
• 400 — validation error; log the response body and correct the source document
• 409 — idempotency conflict; document already processed
• 5xx — retry with exponential backoff; the PSB also retries on delivery failures