Get balance of multiple bitcoin addresses using insight API

GetBitcoinBalances.cs

List<string> lstAddresses = new List<string>() {
    "1Jz6HEKNJpYjXAYRLn49QUUUrizL5qGxjM",
    "1JoktQJhCzuCQkt3GnQ8Xddcq4mUgNyXEa",
    "18vo26nEeDt1Tw17CuWap3F5rKJjBXSMmL",
};

string URL = "https://insight.bitpay.com/api/addrs/utxo";
var request = WebRequest.Create(new Uri(URL)) as HttpWebRequest;
if (request == null)
    throw new Exception("Non HTTP WebRequest");

string strData = "addrs=" + string.Join(",", lstAddresses);
byte[] data = Encoding.ASCII.GetBytes(strData);

request.Method = "POST";
request.Timeout = 15000;
request.ContentType = "application/x-www-form-urlencoded";
request.ContentLength = data.Length;

var reqStream = request.GetRequestStream();
reqStream.Write(data, 0, data.Length);
reqStream.Close();

var response = request.GetResponse();
var resStream = response.GetResponseStream();
var resStreamReader = new StreamReader(resStream);
var resString = resStreamReader.ReadToEnd();

decimal balance = 0;
Newtonsoft.Json.Linq.JContainer results = JsonConvert.DeserializeObject<dynamic>(resString);
if (results is JArray)
{
    foreach (JContainer utxo in results)
    {
        balance += (decimal)utxo["amount"];
    }
    System.Windows.Forms.MessageBox.Show("balance: " + balance);
}