c#多线程2个托管只跑了一个

Question

当执行了下属代码后进度条能够正常运行，label1.text并没有根据x值的变化连续变化

 using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Threading;

namespace WindowsFormsApplication6
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        DateTime dt;
        int x = 0;
        int y = 0;
        private void button1_Click(object sender, EventArgs e)
        {
            timer1.Enabled = true;
            x = 0;
            Thread myThread = new Thread(DoData);
            Thread myThread1 = new Thread(Viewlabel);
            myThread.IsBackground = true;
            myThread1.IsBackground = true;
            myThread1.Start(int.Parse(textBox1.Text));
            myThread.Start(int.Parse(textBox1.Text)); 


            dt = DateTime.Now;
        }




        private delegate void ViewlabelDelegate(object number);
        private void Viewlabel(object number)
        {
            int i = 1, sum = 0;
            if (label1.InvokeRequired)
            {
                ViewlabelDelegate v = Viewlabel;
                label1.Invoke(v, number);
            }
            else
            {
                bool flag = true;
                while (flag)
                {

                    flag = y < (int)number;

                    sum += i++;
                    label1.Text = sum.ToString();
                    Application.DoEvents();
                }
                MessageBox.Show(sum.ToString());
            }

        }

        private delegate void DoDataDelegate(object number);
        /// <summary>
        /// 进行循环
        /// </summary>
        /// <param name="number"></param>
        private void DoData(object number)
        {
            if (progressBar1.InvokeRequired)
            {
                DoDataDelegate d = DoData;
                progressBar1.Invoke(d, number);
            }
            else
            {
                progressBar1.Maximum = (int)number;
                bool flag = true;
                while (flag)
                {

                    flag = x < (int)number;

                    progressBar1.Value = x;

                    Application.DoEvents();
                }
                MessageBox.Show(DateTime.Now.Subtract(dt).ToString());  //循环结束截止时间
            }
        }

        private void timer1_Tick(object sender, EventArgs e)
        {
            x = x + 1;
            y = y + 1;
        }
    }
}

当把Viewlabel代码改为下面代码后sum正常计数

 private void Viewlabel(object number)
{
    int i = 1, sum = 0;

        while (x < (int)number)
        {
            sum += i++;

            Application.DoEvents();
        }
        MessageBox.Show(sum.ToString());

Answer 1

if (xxxx.InvokeRequired)是判断是否跨线程，
else后面是调用控件所在线程，也就是主线程来执行的，你将子线程的任务放到主线程上执行了。
所以你才会用到 Application.DoEvents()