C#中，怎么在“自动分配IP和DNS”与“固定IP和DNS”两种状态中动态切换

C#中，如何在“自动分配IP和DNS”与“固定IP和DNS”两种状态中动态切换？
在网络上找到一些动态设置IP和DNS的代码，都试验成功了。但把它切换为“动态分配IP和DNS”时，却不成功？不知道是否是代码错了，还是缺少一些代码？

C# code

static void SwitchToDHCP()        {            ManagementBaseObject inPar = null;            ManagementBaseObject outPar = null;            ManagementClass mc = new ManagementClass("Win32_NetworkAdapterConfiguration");            ManagementObjectCollection moc = mc.GetInstances();            foreach (ManagementObject mo in moc)            {                if (!(bool)mo["IPEnabled"])                    continue;                inPar = mo.GetMethodParameters("EnableDHCP");                outPar = mo.InvokeMethod("EnableDHCP", inPar, null);                break;            }        }

C# code

//自动获取IPpublic void EnableDHCP()         {             foreach (ManagementObject mo in moc)             {                if (!(bool)mo["IPEnabled"]) continue;                if (!(bool)mo["DHCPEnabled"])                {                    iObj = mo.GetMethodParameters("EnableDHCP");                    oObj = mo.InvokeMethod("EnableDHCP", iObj, null);                }            }        }