获取磁盘序列号，出现未将对象引用到设置的实例的问题？

Question

代码如下：
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.Management;namespace Ex189_读取磁盘序列号
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }        private void Form1_Load(object sender, EventArgs e)
        {
            try
            {
                string hardDiskID = null;
                ManagementObjectSearcher searcher = new ManagementObjectSearcher("select * from Win32_logicaldisk");
                foreach (ManagementObject id in searcher.Get())
                {
                    hardDiskID = id.GetPropertyValue("VolumeSerialNumber").ToString().Trim();
                    this.label1.Text += string.Format("磁盘序列号为{0}    \t\n", hardDiskID);
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }   
    }
}

Answer 1

//获取硬盘的物理id号
public static string getDiskMac()
{
try
{  
string HDid = null;  
ManagementClass cimobject = new ManagementClass("Win32_DiskDrive");   
ManagementObjectCollection moc = cimobject.GetInstances();   
foreach(ManagementObject mo in moc)   
{   
HDid = (string)mo.Properties["PNPDeviceID"].Value;  
break;
}
return HDid;
}
catch
{
return "";
}
}

Answer 2

对于一些比如光驱之类的介质，当还没有被加载时，GetPropertyValue("VolumeSerialNumber")会返回null，直接ToString()自然会报错。
object o = id.GetPropertyValue("VolumeSerialNumber");
if(o != null)
{
    hardDiskID = o.ToString().Trim();
    this.label1.Text += string.Format("磁盘序列号为{0} \t\n", hardDiskID);
}

Answer 3

  private List<string> GetMoc()
            {
                List<string> str_list = new List<string>();
                ManagementClass mcCpu = new ManagementClass("win32_Processor");
                //ManagementObjectCollection mocCpu = mcCpu.GetInstances();
                //foreach (ManagementObject m in mocCpu)
                //{
                //    str[0] = m["ProcessorId"].ToString();
                //}                ManagementClass mcHD = new ManagementClass("win32_logicaldisk");
                ManagementObjectCollection mocHD = mcHD.GetInstances();
                foreach (ManagementObject m in mocHD)
                {
                   
                    str_list.Add(m["DeviceID"].ToString() + ":" + m["VolumeSerialNumber"].ToString());
                }
                return str_list;
            } List<string> test = GetMoc();
                /*
                 *  [0] "C::20201C3B" string
                [1] "D::DC0CE786" string
                [2] "E::100ABEE6" string
                [3] "F::3A104FF1" string                 */