public class DataWrite
 {
  public delegate void UpdateUI(int step);//声明一个更新主线程的委托
  public UpdateUI UpdateUIDelegate;

  public delegate void AccomplishTask();//声明一个在完成任务时通知主线程的委托
  public AccomplishTask TaskCallBack;
  
  public void Write(object lineCount)
  {
   StreamWriter writeIO = new StreamWriter("text.txt", false, Encoding.GetEncoding("gb2312"));
   string head = "编号,省,市";
   writeIO.Write(head);
   for (int i = 0; i < (int)lineCount; i++)
   {
    writeIO.WriteLine(i.ToString() + ",湖南,衡阳");
    //写入一条数据，调用更新主线程ui状态的委托
    UpdateUIDelegate(1);
   }
   //任务完成时通知主线程作出相应的处理
   TaskCallBack();
   writeIO.Close();
  }
 }

delegate void AsynUpdateUI(int step);

  private void btnWrite_Click(object sender, EventArgs e)
  {
   int taskCount = 10000; //任务量为10000
   this.pgbWrite.Maximum = taskCount;
   this.pgbWrite.Value = 0;

   DataWrite dataWrite = new DataWrite();//实例化一个写入数据的类
   dataWrite.UpdateUIDelegate += UpdataUIStatus;//绑定更新任务状态的委托
   dataWrite.TaskCallBack += Accomplish;//绑定完成任务要调用的委托

   Thread thread = new Thread(new ParameterizedThreadStart(dataWrite.Write));
   thread.IsBackground = true;
   thread.Start(taskCount);
  }

  //更新UI
  private void UpdataUIStatus(int step)
  {
   if (InvokeRequired)
   {
    this.Invoke(new AsynUpdateUI(delegate(int s)
    {
     this.pgbWrite.Value += s;
     this.lblWriteStatus.Text = this.pgbWrite.Value.ToString() + "/" + this.pgbWrite.Maximum.ToString();
    }), step);
   }
   else
   {
    this.pgbWrite.Value += step;
    this.lblWriteStatus.Text = this.pgbWrite.Value.ToString() + "/" + this.pgbWrite.Maximum.ToString();
   }
  }

  //完成任务时需要调用
  private void Accomplish()
  {
   //还可以进行其他的一些完任务完成之后的逻辑处理
   MessageBox.Show("任务完成");
  }