Threading Error - Dispatcher?

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Printing;
using System.Threading;
using System.ComponentModel;

namespace ThreadAndSpool
{
    class MyMainProcessClass
    {
        MyBackgrounWorkerClass bw = new MyBackgrounWorkerClass();
        public MyMainProcessClass()
        {
            bw.Start();
        }
    }

    class MyBackgrounWorkerClass
    {
        private BackgroundWorker _bw = new BackgroundWorker();
        private PrintHost _ph;

        public MyBackgrounWorkerClass()
        {
            _ph = new PrintHost();
            _bw.DoWork += new DoWorkEventHandler(bw_DoWork);
        }

        private void bw_DoWork(object sender, DoWorkEventArgs e)
        {
            _ph.CheckHost();
        }

        public void Start()
        {
            _bw.RunWorkerAsync();
        }
    }

    class PrintHost
    {
        public PrintServer _hostingServer;
        public PrintHost()
        {
            _hostingServer = new PrintServer(@"\\" + Environment.MachineName, PrintSystemDesiredAccess.AdministrateServer);
        }

        public void CheckHost()
        {
            _hostingServer.Refresh();
        }
    }
}

_hostingServer.Refresh();

"The calling thread cannot access this object because a different thread owns it."