string moduleName = Process.GetCurrentProcess().MainModule.ModuleName;

            string processName = System.IO.Path.GetFileNameWithoutExtension(moduleName);

            Process[] processes = Process.GetProcessesByName(processName);

            if (processes.Length > 1)

            {

                MessageBox.Show("程序已经运行！", "信息提示", MessageBoxButtons.OK, MessageBoxIcon.Information);

                this.Close();

            }

      这段代码确实有种变相的单例模式的味道，不过好象一段代码，缺少了点AI的味道，应该把当前的那个实例调用出来就会更好了．．．