C#

using junkie;

namespace junk
{
    public enum Output_State
    {
        OFF,
        ON,
        Dont_Care,
    }

    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        public void button1_Click(object sender, EventArgs e)
        {
            ClassTwo testClassTwo = new ClassTwo();
            testClassTwo.TestMethod(Output_State.Dont_Care);
        }
    }

    public class ClassTwo
    {
        junkie.NewClass1 testClassThree = new junkie.NewClass1();

        public void TestMethod(Output_State output)
        {
            testClassThree.TestMethod(output);
        }
    }
}

namespace junkie
{
    public enum Output_State
    {
        OFF,
        ON,
        Dont_Care,
    }

    class NewClass1
    {
        public void TestMethod(Output_State output)
        {
            switch (output)
            {
                case Output_State.ON: MessageBox.Show("ON"); break;
                case Output_State.OFF: MessageBox.Show("OFF"); break;
                case Output_State.Dont_Care: MessageBox.Show("Don't Care"); break;
                default: MessageBox.Show("HUH?"); break;
            }
        }
    }
}

using System;
using System.ServiceProcess;
using System.Threading;

public class Application
{
    // These should be private fields, but I don't care about that now...
    public bool running = true;
    public bool terminated = false;

    public void MainLoop()
    {
        while(running)
        {
            ReadData();   // This method may take several minutes to complete
            ExportData();
        }

        terminated = true;
    }

    private void ReadData()
    {
        // Do some work which may take time, several minutes

        // Let say this method takes 3 minutes to complete
    }
    
    private void ExportData()
    {
        // Export data
    }
}

public partial class Service: ServiceBase
{
    Application application;

    public Service()
    {
        InitializeComponent();
    }

    public OnStart()
    {
        this.application = new Application();

        Thread mainLoopThread = new Thread(application.MainLoop);
        mainLoopThread.Start();
    }

    public OnStop()
    {
        applicaiton.running = false;

        while(application.terminated == false)
        {
            this.RequestAdditionalTime(1000);
        }
    }
}