static class Program
    {
        /// <summary>
        /// 應用程序的主入口點。
        /// </summary>
        [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            //Application.Run(new Form1());
 

            Form1 mainForm = new Form1();
            mainForm.StartPosition = FormStartPosition.CenterScreen;
            Application.Run(mainForm);
        }
    }

C#窗口居中顯示