backgroundworker控件等待执行完毕问题（没有耐心的人千万别看）

初次使用 backgroundworker控件 
想让backgroundworker执行一个方法，不过方法执行的时间比较长大概有几十秒想要实现：
当用户单击退出按钮的时候，检查backgroundworker控件是否正在执行
如果正在执行，则等待backgroundworker执行完毕
最后退出
技术难点： 
    等待backgroundworker执行完毕 
目前代码：
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Threading;namespace backgroundWorkDemo
{
    public partial class Form1 : Form
    {
        private int second = 10;
        private DateTime startTime;
        private bool bgwOver1 = true;
        private bool bgwOver2 = true;        private delegate void SetTextHandler(string text);        private System.Timers.Timer timer1 = new System.Timers.Timer();
        private System.Timers.Timer timer2 = new System.Timers.Timer();        public Form1()
        {
            InitializeComponent();
        }        public void SetText(string text)
        {
            if (this.richTextBox1.InvokeRequired)
            {
                this.richTextBox1.Invoke(new SetTextHandler(SetText), new object[] { text });
            }
            else
            {
                this.richTextBox1.Text += text + "\r\n";
            }
        }        private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
        {
            if (this.bgwOver1)
            {
                this.bgwOver1 = false;
                this.Run("第一个线程");
            }
        }        private void Run(string name)
        {
            while (startTime.AddSeconds(second) >= DateTime.Now)
            {                this.SetText(DateTime.Now.ToString() + "\t" + name);
            }
        }        private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
        {
            //this.richTextBox1.Text += "操作完成";
            this.SetText("第一个线程操作完成");
            this.bgwOver1 = true;
        }        private void btnStart_Click(object sender, EventArgs e)
        {
            this.btnStart.Enabled = false;
            this.startTime = DateTime.Now;
            this.timer1.Interval = 2000;
            this.timer1.Enabled = true;
            this.timer1.Elapsed += new System.Timers.ElapsedEventHandler(timer1_Elapsed);            this.timer2.Interval = 2000;
            this.timer2.Enabled = true;
            this.timer2.Elapsed += new System.Timers.ElapsedEventHandler(timer2_Elapsed);            
        }        void timer2_Elapsed(object sender, System.Timers.ElapsedEventArgs e)
        {
            this.backgroundWorker2.RunWorkerAsync();
        }        void timer1_Elapsed(object sender, System.Timers.ElapsedEventArgs e)
        {
            this.backgroundWorker1.RunWorkerAsync();
        }        private void btnStop_Click(object sender, EventArgs e)
        {
            this.btnStop.Enabled = false;
            this.backgroundWorker1.CancelAsync();  
        }        private void btnDispose_Click(object sender, EventArgs e)
        {
            this.btnDispose.Enabled = false;
            this.backgroundWorker1.Dispose();
        }        private void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
        {
            this.progressBar1.Value = e.ProgressPercentage;
        }        private void btnExit_Click(object sender, EventArgs e)
        {
            this.timer1.Enabled = false;
            this.timer2.Enabled = false;            //等待backgroundworder执行完毕
            while (this.backgroundWorker1.IsBusy)
            {
                Application.DoEvents();
            }
            while (this.backgroundWorker2.IsBusy)
            {
                Application.DoEvents();
            }
            //
            this.richTextBox1.Text += "\r\n停止完成";
        }        private void backgroundWorker2_DoWork(object sender, DoWorkEventArgs e)
        {
            if (this.bgwOver2)
            {
                this.bgwOver2 = false;
                this.Run("第二个线程");
            }
        }        private void backgroundWorker2_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
        {
            this.bgwOver2 = true;
            this.SetText("第二个线程操作完成");
        }
    }
}解决代码：            //等待backgroundworder执行完毕
            while (this.backgroundWorker1.IsBusy)
            {
                Application.DoEvents();
            }
            while (this.backgroundWorker2.IsBusy)
            {
                Application.DoEvents();
            }
            //现有解决方案在停止应用程序时会出现CPU占用率很高的情况能否有种方法既能解决等待问题又能够解决CPU占用问题？
希望大家各抒己见！