C# 多线程更新界面的错误的解决方法

目录

由于一个线程的程序，如果调用一个功能是阻塞的，那么就会影响到界面的更新，导致使用人员操作不便。所以往往会引入双线程的工作的方式，主线程负责更新界面和调度，而次线程负责做一些阻塞的工作。

这样做了之后，又会导致一个常见的问题，就是很多开发人员会在次线程里去更新界面的内容。比如下面的例子：

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

namespace WindowsFormsApp1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            var thread2 = new System.Threading.Thread(WriteTextUnsafe);
            thread2.Start();
        }

        private void WriteTextUnsafe() =>
            textBox1.Text = "This text was set unsafely.";
    }
}

这里就是使用线程来直接更新界面的内容，就会导致下面的出错：

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

namespace WindowsFormsApp1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            var threadParameters = new System.Threading.ThreadStart(
                delegate { WriteTextSafe("This text was set safely."); });
            var thread2 = new System.Threading.Thread(threadParameters);
            thread2.Start();
        }

        public void WriteTextSafe(string text)
        {
            if (textBox1.InvokeRequired)
            {
                // Call this same method but append THREAD2 to the text
                Action safeWrite = delegate { WriteTextSafe($"{text} (THREAD2)"); };
                textBox1.Invoke(safeWrite);
            }
            else
                textBox1.Text = text;
        }
    }
}