How can I dynamically use address variable fr geocode in C# for getting

public static List GetAddressesByKeyword(string keyword , string address = null)

    {
        var parameters = new Dictionary<string, string>()
        {  
            {"address", " 836 Kilbridge Lane, Coppell, TX" },
            {"input",keyword.Replace(" ", "+") },
            {"types", "geocode" },
            {"key", ConfigurationManager.AppSettings["GoogleApiKey"]}
        };

       if (!String.IsNullOrWhiteSpace(address))
        parameters["address_components"] = String.Format("address{0}", address.ToLower());

        var queryString = String.Join("&", parameters.Select(kv => kv.Key + "=" + kv.Value));

        var webRequest = WebRequest.Create("http://maps.googleapis.com/maps/api/geocode/json?" + queryString );
 var webResponse = webRequest.GetResponse();
            var items = new List<googleaddressmodel>();

            using (var reader = new StreamReader(webResponse.GetResponseStream(), Encoding.UTF8))
            {
                var content = reader.ReadToEnd();
                var mapItem = JsonConvert.DeserializeObject<googlegeocoderesponse>(content);
                if (mapItem.status.ToLower() == "ok")
                {
                    foreach (var r in mapItem.results)
                    {
                        items.Add(ResultToModel(r));
                    }
                }
            }
            return items;
        }