C# 如何写代码提取电脑开机时间

private void button1_Click(object sender, EventArgs e)
{
int hm = System.Environment.TickCount;
double h = hm / 3600000.0;
double m =double.Parse("0."+h.ToString("F6").Substring(h.ToString().IndexOf(".")+1))*60;
double s = double.Parse("0." + m.ToString("F6").Substring(m.ToString().IndexOf(".") + 1)) * 60;
string h1 = ((int)h).ToString();
string m1 = ((int)m).ToString();
string s1 = ((int)s).ToString();
if ((int)h < 10) h1 = "0"+h1;
if ((int)m < 10) m1 = "0"+m1;
if ((int)s < 10) s1 = "0"+s1;
string nowtime = DateTime.Now.TimeOfDay.ToString().Substring(0,8);
string span = h1 + ":" + m1 + ":" + s1;
TimeSpan spantime = Convert.ToDateTime(nowtime).Subtract(Convert.ToDateTime(span));
MessageBox.Show("您的开机时间是： "+spantime.ToString());
}

给分吧，用了我一个多小时才写出来，嘿嘿<