C# WMI SetMTU System.ManagementException

Question

We are working on a programm to configure some NICs. We have to change IP Adresses, Subnetmask and the MTU. Everything went well except the MTU Statement:

public void SetMTU()
{
    ManagementClass objMC = new ManagementClass("Win32_NetworkAdapterConfiguration");
    ManagementObjectCollection objMOC = objMC.GetInstances();
    foreach (ManagementObject objMO in objMOC)
    {
       if (networkadapterID == (String)objMO["SettingID"])
          {                
               ManagementBaseObject setMTU;
               ManagementBaseObject newMTU = objMO.GetMethodParameters("SetMTU");
               Int32 test = 9216;
               newMTU["MTU"] = test;
               setMTU = objMO.InvokeMethod("SetMTU", newMTU, null);
          }  
    }
}

The correct NIC ID is given. Other WMI Operations succeed but we stuck on that one with error Message: System.Management.ManagementException: "Die Methode ist ungültig. "

(System.Management.ManagementException: "The Method is invalid.")

We have also tried to use "test" as string or uint32 (because the microsoft docs says it's an uint32),also:

newMTU["MTU"] = new (u)int[] { MTU };

but it doesnt work either. Meanwhile we don't have any ideas how to fix the problem.

I am grateful for every idea.

Thanks for your help and have a good day, Alex

Edit: Code to read the MTU should be (you have to tell this part a NetworkID so you don't read the Value of every NIC, you find this in your registry, but you should be able to delete the if part):

ManagementClass objMC = new ManagementClass("Win32_NetworkAdapterConfiguration");
ManagementObjectCollection objMOC = objMC.GetInstances();
foreach (ManagementObject objMO in objMOC)
{
    if (networkadapterID == (String)objMO["SettingID"])
    {
        MessageBox.Show(Convert.ToString(objMO["MTU"]) + ": " + Convert.ToString(objMO["SettingID"]));
    }
}

Answer 1

So far we didn't get the problem solved but we now check if the OS is Windows 10 and we will start a PowerShell task with this command:

Get-NetAdapterAdvancedProperty -Name 'NICName' -DisplayName 'Jumbo-Rahmen' | Set-NetAdapterAdvancedProperty -RegistryValue  'MTUsize';

Jumbo-Rahmen should be JumboPacket on an English OS

If the OS is not Windows 10 the User will be asked to change the MTU manually