Call the Delivery Zone API from .NET

When to call the API

Call the API from your ASP.NET controller or service layer before confirming the order. Never expose the API key or route the call through the client.

Request example

// .NET / C# — server-side, inject via IHttpClientFactory
var payload = new {
  destinationPostcode = postcode,
  basketValueCents = basketCents,
};
var response = await _http.PostAsJsonAsync(
  "https://api.deliveryzone.fi/v1/check", payload);
var data = await response.Content.ReadFromJsonAsync<CheckResult>();
if (!data.CanDeliver) {
  return BadRequest(data.Reason);
}

Error handling

When canDeliver is false, the response includes a reason field. Display this to the customer:

• OUT_OF_ZONE — postcode is valid but outside all defined zones
• UNKNOWN_POSTCODE — postcode is not recognised
• MIN_BASKET — basket value is below the zone minimum

Always handle HTTP errors (5xx, timeout) gracefully. If the API is unreachable, fail safe — either reject the order or allow manual review.

Production checklist

• Inject HttpClient via dependency injection (IHttpClientFactory)
• Store API key in environment variables or user secrets
• Handle HTTP errors and timeouts with try/catch
• Test with sandbox key first
• Confirm rejection behaviour in your staging environment

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