csharp paralel requests.

Paralel.cs

       public static async Task<string> CalculateDistance(string origins, string destination)
        {
            string url = string.Format(urlBase, origins, destination);
            RestClient client = new RestClient(url);

            var request = new RestRequest();
            var response = await client.ExecuteGetTaskAsync(request);

            DistanceModel model = JsonConvert.DeserializeObject<DistanceModel>(response.Content);

            var firstOrDefault = model.Rows.FirstOrDefault();
            Elements orDefault = firstOrDefault?.Elements.FirstOrDefault();
            if (orDefault != null)
                return orDefault.Duration.Text;

            return string.Empty;
        }
        
        public async Task<HttpResponseMessage> CalculateParallel(DistanceCalculationModel model)
        {
            HttpResponseMessage message;

            var allTasks = from station in model.Stations
                           select DistanceMatrixCalculator.CalculateDistance(model.Origin,station.Lat+","+station.Lng);

            string[] results = await Task.WhenAll(allTasks);

            message = Request.CreateResponse(HttpStatusCode.OK, results);

            return message;
        }