在窗体中添加两个Lable控件和一个Button控件。单击Button控件在两个Lable控件中显示计算结果。代码是：
using System;
using System.Collections.Generic;
using
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Threading;

namespace LXK
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        Thread th1, th2;
        double x1, x2;

        private void button1_Click(object sender, EventArgs e)
        {
            th1 = new Thread(new ThreadStart(fangfa1));
            th2 = new Thread(new ThreadStart(fangfa2));
            th1.Start();
            th2.Start();
        }

        private void fangfa1()
        {
            for (int i = 0; i < 50; i++)
            {
                x1 = i * 2;
                label1.Text += x1.ToString();
            }
        }

        private void fangfa2()
        {
            for (int i = 0; i < 50; i++)
            {
                x2 = i + 2;
                label2.Text += x2.ToString();
            }
        }

        private void Form3_Load(object sender, EventArgs e)
        {
            button1.Text = "OK";
            label1.BorderStyle = BorderStyle.Fixed3D;
            label2.BorderStyle = BorderStyle.FixedSingle;
        }
    }
}
运行提示错误，请帮忙解决下。谢谢。

那个没有改过来。是在From3中写的，在From1中调用的。调用那部分没写，把它改了下，没改彻底。很抱歉。

该如何调用委托？