VMWare VIM SDK .Net, update CustomFieldValue

Hi,

I am not sure if this is the correct forum for SDK questions, please redirect me to a correct one if not, but here goes:

I have this code:

public void SetFieldValue(int key, string value)

{

    var customField = (CustomFieldStringValue)this.VirtualMachine.CustomValue.Single(cv => cv.Key == key);

    customField.Value = value;

}

That in itself works, as in, it's visible that the value has changed, but I don't see it reflected upon the actual custom field on the VM when viewed in the vSphere Client.

So, is there a save I need to do, or do I have to change the value in another fashion?

Thanks