public class Student
    {
        //创建单例类，内部静态类方法
        private Student() { }//私有构造函数
        class Nested
        {
            internal static readonly Student instance = new Student();
        }
        public static Student Instance
        {
            get { return Nested.instance; }
        }

        //创建字段和其属性
        private string name;
        public string  Name
        {
            get { return name; }
            set { name = value; }
        }
        private int chinses;

        public int Chinses
        {
            get { return chinses; }
            set { chinses = value; }
        }
        private int math;

        public int Math
        {
            get { return math; }
            set { math = value; }
        }
    }

        public Setting()
        {
            InitializeComponent();
        }
        Student stu= Student.Instance; //创建单例类的对

        private void Setting_Load(object sender, EventArgs e)
        {
           
        }

        private void BtnChange_Click(object sender, EventArgs e)
        {
            stu.Name = this.textBoxName.Text;//把子窗体textbox显示值赋给字段的属性
            stu.Chinses = Convert.ToInt32(this.textBoxChinese.Text);
            stu.Math = Convert.ToInt32(this.textBoxMath.Text);
        }

Student stu = Student.Instance;//创建单例类
        private void MainForm_Load(object sender, EventArgs e)
        {
            this.tBName.Text = "Weber";//主窗体加载显示内容
            this.tBChinese.Text = Convert.ToString(89);
            this.tBMath.Text = Convert.ToString(90);
        }

        private void ToolStripButton1_Click(object sender, EventArgs e)
        {
            Setting mySetting = new Setting();
            mySetting.ShowDialog();//子窗体弹出

            this.tBName.Text = stu.Name;//字段属性的值赋给textbox值
            this.tBMath.Text = Convert.ToString(stu.Math);
            this.tBChinese.Text = Convert.ToString(stu.Chinses);

        }