C#中listbox删除出现未将对象引用设置到对象实例
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;
using System.Threading;
namespace Error
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
public void Ad(string x)
{
if (listBox1.Items.Count > 19)
{
if(!string.IsNullOrEmpty(listBox1.Items[listBox1.Items.Count - 1].ToString()))
{
listBox1.Items.RemoveAt(listBox1.Items.Count - 1);
}
}
listBox1.Items.Insert(0, x);
}
private void button1_Click(object sender, EventArgs e)
{
Thread A1;
Thread A2;
Thread A3;
Thread A4;
Control.CheckForIllegalCrossThreadCalls = false;
A1 = new Thread(new ThreadStart(AutoPic1));
A1.Start();
Control.CheckForIllegalCrossThreadCalls = false;
A2 = new Thread(new ThreadStart(AutoPic2));
A2.Start();
Control.CheckForIllegalCrossThreadCalls = false;
A3 = new Thread(new ThreadStart(AutoPic3));
A3.Start();
Control.CheckForIllegalCrossThreadCalls = false;
A4 = new Thread(new ThreadStart(AutoPic4));
A4.Start();
}
public void AutoPic1()
{
for (int i = 0; i < 100; i++)
{
Ad(i + "");
Thread.Sleep(200);
}
}
public void AutoPic2()
{
for (int i = 0; i < 100; i++)
{
Ad(i + "");
Thread.Sleep(200);
}
}
public void AutoPic3()
{
for (int i = 0; i < 100; i++)
{
Ad(i + "");
Thread.Sleep(200);
}
}
public void AutoPic4()
{
for (int i = 0; i < 100; i++)
{
Ad(i + "");
Thread.Sleep(200);
}
}
}
}
完整代码如上，他是有时出现这问题，有时没出现，求帮助
[解决办法]
你没有线程同步，当你删除了一个，导致list数量紊乱，线程中再访问时，就会出现访问不到的情况
[解决办法]
public void Ad(string x)
{
lock (listBox1)
