Получить серийный номер жесткого диска

I want to get hard disk serial number. How I can I do that? I tried with two code but I am not getting

StringCollection propNames = new StringCollection();
ManagementClass driveClass = new ManagementClass("Win32_DiskDrive");
PropertyDataCollection  props = driveClass.Properties;
foreach (PropertyData driveProperty in props) 
{
    propNames.Add(driveProperty.Name);
}
int idx = 0;
ManagementObjectCollection drives = driveClass.GetInstances();
foreach (ManagementObject drv in drives)
       {
          Label2.Text+=(idx + 1);
          foreach (string strProp in propNames)
           {
            //Label2.Text+=drv[strProp];
         Response.Write(strProp + "   =   " + drv[strProp] + "</br>");
          }
    }

In this one I am not getting any Unique Serial number.
And Second one is

string drive = "C";
ManagementObject disk = new ManagementObject("win32_logicaldisk.deviceid=\"" + drive + ":\"");
disk.Get();
Label3.Text = "VolumeSerialNumber="+ disk["VolumeSerialNumber"].ToString();

Here I am getting VolumeSerialNumber. But it is not unique one. If I format the hard disk, this will change. How Can I get this?