如何在文本文件中保存应用程序的启动和关闭时间？

Question

Just this - whlie running its showing error: Object reference not set to an instance of an object

please help

what is it means? instead of that which code should I use?

using System;
using System.Windows.Forms;
using System.Text;
using System.IO;

namespace Charts
{
System.Timers.Timer myTimer = new System.Timers.Timer();
public partial class Form1 : Form
{
    private StringBuilder sb;
    public Form1()
    {
        InitializeComponent();
    }

private void Form1_Load(object sender, EventArgs e)
    {
      try {  
        this.chart1.Series["Performance"].Points.AddXY("me", 44);
        this.chart1.Series["Performance"].Points.AddXY("Year", 66);
        this.chart1.Text.Clone();
        timer1.Start();

        File.WriteAllText(String.Format(@"D:\Log at {0:yyyy-MM-dd HH:mm:ss}.txt", DateTime.Now), sb.ToString());
     }   
    catch (Exception ex)
        { MessageBox.Show(ex.Message); }
    }
}
}

Answer 1

You have an object not initialized. Probably your StringBuilder sb or your timer.

You should have a line with something like

sb = new StringBuilder();

Answer 2

在调用timer1.start（）之前，必须在某个地方初始化timer1