System.Threading.Mutex
System.Threading.ManualResetEvent
System.Threading.Semaphore

VD>System.Threading.Mutex
VD>System.Threading.ManualResetEvent
VD>System.Threading.Semaphore
VD>

while(... )
{

нечто.... 

}

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Threading;
using System.Data.SqlClient;
using System.Configuration;

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

        private void dataGridView1_CellContentClick(object sender, DataGridViewCellEventArgs e)
        {

        }
        private BackgroundWorker worker = null;
        const int interval = 5000;
        private void Form1_Load(object sender, EventArgs e)
        {           
            worker = new BackgroundWorker();
            worker.WorkerSupportsCancellation = true;
            worker.DoWork += new DoWorkEventHandler(worker_DoWork);
            worker.RunWorkerAsync(interval);
        }

        private void customersBindingSource_CurrentChanged(object sender, EventArgs e)
        {

        }

        private void button1_Click(object sender, EventArgs e)
        {
            refreshData();
        }
        private void checkBox1_CheckedChanged(object sender, EventArgs e)
        {
            if (checkBox1.Checked)
            {
                if (!worker.IsBusy)
                    worker.RunWorkerAsync(interval);
            }
            else {
                if (worker.IsBusy)
                    worker.CancelAsync();
            }
        }
        private void refreshData()
        {
            string strL = this.label1.Text;
            this.label1.Text = "retrieving data...";
            Application.DoEvents();
            this.customersTableAdapter.Fill(this.northwindDataSet.Customers);
            this.label1.Text = strL;
        }

        static int Counter = 0;
        SqlConnection connection = null;
        SqlCommand command = null;
        string key = "customers";
        int changeID = -1;

        void worker_DoWork(object sender, DoWorkEventArgs e)
        {
            connection = new SqlConnection(System.Configuration.ConfigurationManager.AppSettings["SQLForms.Properties.Settings.NorthwindConnectionString"]);
            command = new SqlCommand("getChangeNotifications", connection);
            command.CommandType = CommandType.StoredProcedure;

            connection.Open();
            while (true)
            {
                if (InvokeRequired)
                {
                    // Deal with possible cancellation
                    if (worker.CancellationPending == true)
                    {
                        e.Cancel = true;
                        break;
                    }
                    // bool dirty = (Counter % 5 == 0);
                    bool dirty = worker_Poll();
                    Invoke(new Change(OnChange), dirty);
                    System.Threading.Thread.Sleep((int)e.Argument);
                }
            }
            connection.Close();
        }
        private void OnChange(bool dirty)
        {
            this.label2.Text = (++Counter).ToString();
            if (dirty)
            {
                this.refreshData();
            }
            else
                Application.DoEvents();
        }

        private delegate void Change(bool dirty);

        #region DB Poll
        bool worker_Poll()
        {
            bool dirty = false;
            SqlDataReader reader;
            reader = command.ExecuteReader();
            while (reader.Read())
            {
                if (key == reader["Table"].ToString())
                {
                    int cid = (int)reader["ChangeID"];
                    if (changeID != cid)
                    {
                        changeID = cid;
                        dirty = true;
                    }
                    break;
                }
            }
            reader.Dispose();
            reader.Close();
            return dirty;
        }
        #endregion

        private void button2_Click(object sender, EventArgs e)
        {
            ColorDialog dlg = new ColorDialog();
            dlg.ShowDialog();
            dlg.Dispose();
        }

    }
}

public void OnSocketDataReceived(object socketData)
{
  // отображение полученных данных в форме
}

public void OnSocketDataReceived(object socketData)
{
  Invoke(new VisualUpdate(OnVisualUpdate), new object[]{socketData});
}

public delegate void VisualUpdate(object data);

public void OnVisualUpdate(object data)
{
  // отображение полученных данных в форме
}