HTTP triggered function

HttpTriggeredFunction.csx

#r "Newtonsoft.Json"
using System;
using System.Configuration;
using Newtonsoft.Json;
using System.Net;

// These are the (interesting parts) of the models returned from the kolonial API.
// The actual JSON returned contains more properties, but I see no reason to bother the deserializer
// with more than what we actually need.
public class KolonialSearchResponse {
    public KolonialProduct[] Products {get;set;}
}

public class KolonialProduct {
    public string Id {get;set;}
    public string Barcode { get; set; }
    public string Brand {get; set;}
    public string Name {get; set;}
}

static HttpClient HttpClient = null;

public static async Task<HttpResponseMessage> Run(HttpRequestMessage req, TraceWriter log)
{
    if(HttpClient == null)
        HttpClient = CreateHttpClient(log);

    string barcode = GetBarcodeFromRequest(req);

    // Request product from kolonial
    var httpResult = await HttpClient.GetAsync("https://kolonial.no/api/v1/search/?q=" + barcode);
    if (!httpResult.IsSuccessStatusCode)
    {
        // not much we can do here, so just log the error and return an error status code.
        log.Error($"Error occured when getting data from kolonial."); 
        return req.CreateErrorResponse(HttpStatusCode.InternalServerError, "Product not found");
    }
    else
    {
        var json = await httpResult.Content.ReadAsStringAsync();
        if (json != null)
        {
            log.Info($"Processing JSON: {json}");
            var results = JsonConvert.DeserializeObject<KolonialSearchResponse>(json);

            // If the search call returns anything but a single product
            // we have no idea how to handle it.
            if(results.Products != null && results.Products.Length == 1)
            {
                var product = results.Products.First();
                product.Barcode = barcode;
                return req.CreateResponse(HttpStatusCode.OK, product);
            }
        }
        return req.CreateErrorResponse(HttpStatusCode.BadRequest, "Product not found");
    }
}

public static HttpClient CreateHttpClient(TraceWriter log)
{
    log.Info("Instantiating HTTP client.");
    var httpClient = new HttpClient();
    httpClient.DefaultRequestHeaders.Add("X-Client-Token", ConfigurationManager.AppSettings["KolonialToken"]);
    httpClient.DefaultRequestHeaders.Add("User-Agent", ConfigurationManager.AppSettings["KolonialUserAgent"]);
    return httpClient;
}

public static string GetBarcodeFromRequest(HttpRequestMessage req){
    return req.GetQueryNameValuePairs()
        .FirstOrDefault(q => string.Compare(q.Key, "barcode", true) == 0)
        .Value;
}