1. Create a new console application in a new, empty folder by running dotnet new console.
2. Add a reference for Alpaca .NET SDK with dotnet add package Alpaca.Markets.
3. Change Main method in auto-generated Programm.cs file to this code snippet:

var client = new Alpaca.Markets.RestClient(
    KEY_ID, SECRET_KEY, API_URL);

var clock = client.GetClockAsync().Result;

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

4. Replace KEY_ID, SECRET_KEY and API_URL values with your own data from the Alpaca dashboard.
5. Run the sample application using dotnet run command and check the output. You should see information about the current market timestamp and the times that the market will open and close next.

Starting from version 1.1.0 you can use the IConfiguration interface for providing configuration data to constructors. You can read more about the new .NET Core configuration approach in this article. Please also read the appropriate Wiki pages about expected configuration parameters for each constructor.

Starting from version 1.2.3 and 2.0.0 NuGet packages contains strongly signed assemblies only for .NET Standard 1.6 and 2.0 targets. .NET Framework 4.5 version of Alpaca.Markets.dll is packaged unsigned because a dependent assembly, NATS.Client.dll, also shipped unsigned.

Polygon is deprecating their NATS streaming in favor of Websockets, and they have finally made it possible for Alpaca users to switch to the websocket endpoint. Starting from version 3.2.0-beta2 we mark NatsClient class with Obsolete attribute and any usage of this class will generate warning for now. Recommended way for obtaining real-time data now is PolygonSockClient usage (it provides very similar interface so transition should be easy). In upcoming minor release (most probably 3.3.0) NatsClient will be marked as Obsolete with error generation and in upcoming major release (4.0.0) it will be removed from SDK completely.