namespace ThreadDemo
{
    public partial class Form1 : Form
    {
        private Yan y = new Yan();

        public Form1()
        {
            InitializeComponent();

        }

        private void button1_Click(object sender, EventArgs e)
        {
            Thread t1 = new Thread(T1);
            t1.Name = "t1";
            Thread t2 = new Thread(T2);
            t2.Name = "t2";

            t1.Start();
            t2.Start();
        }

        private void T1()
        {
            lock (y)
            {
                for (int i = 0; i < 10000000; ++i) ;
                y.str = "先";
                MessageBox.Show(y.str);
            }
             
        }

        private void T2()
        {
            y.str = "后";
            MessageBox.Show(y.str);
        }
    }

    public class Yan
    {
        public string str = "";
    }
}