用锁文件的方法来实现只有一个实例运行

public class Program
    ...{
        public Program()
        ...{ 
        }

        private const string lockfile="mylock.txt";
        

        public static void Main()
        ...{
            FileStream fs=null;
            if(File.Exists(lockfile))
            ...{
                try
                ...{
                    fs=File.Open(lockfile,FileMode.Append,FileAccess.Write,FileShare.None); 
                }
                catch(System.IO.IOException ex)
                ...{
                    MessageBox.Show("程序只允许一个实例在运行");
                     
                    System.Environment.Exit(System.Environment.ExitCode);

                }
            }
            else
            ...{
                fs=File.Create(lockfile);
            }

            Form1 tes=new Form1();
            Application.Run(tes);

        }
    }