如何使用WMI获取CPU序列号？

//返回的是一个数组，可能存在多个CPU
using System;
using System.Management;
using System.Collections;
public ArrayList GetCpuID()
{
ArrayList al=new ArrayList();

try
{
ManagementClass mc = new ManagementClass("Win32_Processor");
ManagementObjectCollection moc = mc.GetInstances();


foreach( ManagementObject mo in moc )
{
al.Add(mo.Properties["ProcessorId"].Value.ToString());

}
return al;
}
catch（）
{
return null;
}

}