Come evitare di duplicare l'applicazione Form Main C#

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace TestApp
{
    class Program
    {
        static void Main(string[] args)
        {
            var Process = from p in System.Diagnostics.Process.GetProcesses()
                          where p.ProcessName.StartsWith("TestApp") // Nome della mia App
                          select p;

            if (!(Process.Count() > 1 ))
            {
                Console.Write("Nessuna Altra Istanza ");
            }
            else if (Process.Count() > 1)
            {
                Console.Write("Applicativo gia in esecuzione ");
            }
            Console.ReadKey();
        }
    }
}

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Linq;
using System.Drawing;
using System.Text;
using System.Windows.Forms;


namespace Schedario
{
    public partial class Form1 : Form
    {
        SystemManager oSysManager = new SystemManager();
        static void Main(string[] args)
        {
            var Process = from p in System.Diagnostics.Process.GetProcesses()
                          where p.ProcessName.StartsWith("Form1") // Nome della mia App
                          select p;

            if (!(Process.Count() > 1))
            {
                Console.Write("Nessuna Altra Istanza ");
            }
            else if (Process.Count() > 1)
            {
                Console.Write("Applicativo gia in esecuzione ");
            }
            Console.ReadKey();
        }


        public Form1()
        {
            InitializeComponent();
        }
   }
}