Program.cs

using System;
using System.Configuration;
using Alpaca.Markets;

namespace example
{
    class Program
    {
        static void Main(string[] args)
        {
            var client = new Alpaca.Markets.RestClient(
                "APCA-API-KEY-ID", "APCA-API-SECRET-KEY");

            var clock = client.GetClockAsync().Result;

            if (clock != null)
            {
                Console.WriteLine(
                    "Timestamp: {0}, NextOpen: {1}, NextClose: {2}",
                    clock.Timestamp, clock.NextOpen, clock.NextClose);
            }

            var account = client.GetAccountAsync().Result;
            Console.Write("portfolio_value = {0}", account.PortfolioValue);

            if (clock.IsOpen) {
                var order = client.PostOrderAsync("AAPL", 1,
                                                  OrderSide.Buy, OrderType.Market,
                                                  TimeInForce.Day).Result;
                Console.Write("Ordered 1 share of AAPL at {0}", order.SubmittedAt);
            }
        }
    }
}