How do I display total physical RAM, and BIOS serial in a text box

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C#

I have written a fairly basic program in C#, kind of like a system monitor, which our helpdesk uses in order to quickly get some information from users.

It displays Username, Domain, OS, IP and a few other bits of info.

I have since been asked to extend the functionality to include total RAM and the computer serial number, but no matter what i have tried i cant get it to display in to a text box.

What I have tried:

For the RAM i tried using a performance counter, but this only showed available RAM. So i think i need to use WMI?

For the serial i have this:

public static string GetMotherBoardID()
        {
            string mbInfo = String.Empty;
            ManagementScope scope = new ManagementScope("\\\\" + Environment.MachineName + "\\root\\cimv2");
            scope.Connect();
            ManagementObject wmiClass = new ManagementObject(scope, new ManagementPath("Win32_BaseBoard.Tag=\"Base Board\""), new ObjectGetOptions());

            foreach (PropertyData propData in wmiClass.Properties)
            {
                if (propData.Name == "SerialNumber")
                    mbInfo = String.Format("{0,-25}{1}", propData.Name, Convert.ToString(propData.Value));
            }

            return mbInfo;
            ITHelper.txtSerial.Text = mbInfo.ToString();
        }

Which displays the following error

An object reference is required for the non-static field, method, or property


For the RAM i have tried

private static void DisplayTotalRam()
       {
           string Query = "SELECT MaxCapacity FROM Win32_PhysicalMemoryArray";
           ManagementObjectSearcher searcher = new ManagementObjectSearcher(Query);
           int amount = 0;
           foreach (ManagementObject memo in searcher.Get())
           {
               amount += Convert.ToInt32(Convert.ToInt64(memo["Capacity"]) / 1024 / 1024 / 1024);
               txtRam.Text = amount.ToString();
           }
       }

But i get the same message as above