Receiveing null when using SPFarm.Local

The C# class library project I created contains some some simple code below:

namespace IPY_PublishDLL
{
	public class FormPublisher
	{
		public static void publish(string path)
		{
			SPFarm localFarm = SPFarm.Local;
			if (localFarm == null)
			{
				Console.WriteLine("localFarm is null");
				return;
			}
			Console.WriteLine("localFarm is not null");
		}
	}
}

After successfully compiling the class library project, I tried to call the publish method in anothe console project and the code is also quite simple:

using IPY_PublishDLL;

static void Main(string[] args)
        {

            if (args.Length != 1)
            {
                Console.WriteLine("arguments error!");
                Console.Write("Press Enter to Continue");
                Console.ReadLine();
                return;
            }
            FormPublisher.publish(args[0]);
        }

The console application runs well with the outcoming "localFarm is not null"

However, what I need to do is invoking the dll in a ironpython project.

Here is the ironpython code:

import clr

clr.AddReferenceToFile("IPY_PublishDLL.dll")
from IPY_PublishDLL import FormPublisher

path = "C:\\Users\\Administrator\\Desktop\\ipyForm.xsn"
FormPublisher.publish(path)

I ran it with ipy64.exe and what I got is "localFarm is null"

It confused me a lot.

I have set the Platform target to x64

below is the list of my environment:

windows server 2008 r2

sharepoint 2010,

ironpython,

.net framework 3.5.1