how to get Free Physical Memory of OS using c#?

Hi all,

I want to fetch the FreePhysicalMemory of os using c#,

for this im writing WMI qquery below is my code

ObjectQuery wql = new ObjectQuery("SELECT * FROM Win32_OperatingSystem");

ManagementObjectSearcher searcher = new ManagementObjectSearcher(wql);

ManagementObjectCollection results = searcher.Get();

foreach (var result in results)

{

//Free amount

Free = Convert.ToInt32( result["FreePhysicalMemory"]);

}

but the value i am getting is not matching with task manager's value.currenty i am using window 7 OS.

plz tell me if there is any other way to get accurate value

TIA