c# how to get ram usage on system

ObjectQuery wql = new ObjectQuery("SELECT * FROM Win32_OperatingSystem");
ManagementObjectSearcher searcher = new ManagementObjectSearcher(wql);
ManagementObjectCollection results = searcher.Get();

foreach (ManagementObject result in results)
{
    Console.WriteLine("Total Visible Memory: {0} KB", result["TotalVisibleMemorySize"]);
    Console.WriteLine("Free Physical Memory: {0} KB", result["FreePhysicalMemory"]);
    Console.WriteLine("Total Virtual Memory: {0} KB", result["TotalVirtualMemorySize"]);
    Console.WriteLine("Free Virtual Memory: {0} KB", result["FreeVirtualMemory"]);
}

/* Outputs:
    Total Visible Memory: 25054184 KB
    Free Physical Memory: 17048656 KB
    Total Virtual Memory: 29117416 KB
    Free Virtual Memory: 18637080 KB
*/