C#锁线程

类似于unity碰撞事件，A对象同时触发B、C对象的事件，B、C事件同时调用A方法的问题

    public class Person
    {
        public delegate void ValueChangeDel();
        public event ValueChangeDel valueChangeEvent;

        public void Triger()
        {
            valueChangeEvent();
        }
    }
    public partial class Form1 : Form
    {
        Person p1 = new Person();
        Person p2 = new Person();
        public Form1()
        {
            InitializeComponent();
        }
        string txt = null;
        public int value;
        static object _object = new object();
        private bool isChange = false;

        public void Methord()
        {
            lock (_object)//锁代码块
            {
                if (!isChange)
                {
                    value = -value;
                    txt += value + "\r\n";
                    isChange = true;
                }
                else
                {
                    isChange = false;
                }
            }
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            p1.valueChangeEvent += new Person.ValueChangeDel(Methord);
            p2.valueChangeEvent += new Person.ValueChangeDel(Methord);
        }

        private void numericUpDown1_ValueChanged(object sender, EventArgs e)
        {
            if (numericUpDown1.Value == 2)
            {
                value = (int)numericUpDown1.Value;
                new Thread(() =>
                {
                    p1.Triger();
                }).Start();
                new Thread(() =>
                {
                    p2.Triger();
                }).Start();
            }
            if (numericUpDown1.Value == 4)
            {
                richTextBox1.Text = txt;
            }
        }
    }