Update Custom Record Custom Field ?

Does anyone have sample C# code for update on a custom record custom field ??  Naturally, the sample code in the documentation for using update on a customer record isn't translating over to a custom record.  I certainly wish the documentation contained working sample code !

Here is what I have so far but I'm getting a soapexception was unhandled error.  java.lang.nullpointerException. 

Any help is greatly appreciated !



      public bool GetProductFamilyUsingID(string prodFamInternalID)
        {
            CustomRecord custRec = new CustomRecord();
            CustomRecordRef custRecRef = new CustomRecordRef();
            custRecRef.internalId = prodFamInternalID;
            custRecRef.typeId = "58";
            DoubleCustomFieldRef doubleCustRef = new DoubleCustomFieldRef();
            ReadResponse rr = new ReadResponse();

            try
            {
                rr = _ns.get(custRecRef);

            }
            catch (Exception e)