I can't get node ID use csharp sdk

Hi,I use the sample code to test the C# sdk,but node.Online is not true,I can’t get node.ID,can any body help me? the code like this:
Console.WriteLine(“hello world.”);
ZeroTier.Core.Node node = new ZeroTier.Core.Node();
node.Start();
while (!node.Online)
{
Thread.Sleep(1000);
}
Console.WriteLine(node.Id.ToString(“x16”));