public class PostgreSQLDBWorker : DBInterface
	{

            int DBInterface.DeleteRule(string a_object_type, string a_object_name)
		{
                      if (this.GetDbVersion() <= 10)
                     {
                            return this.OldHandler(a_object_type, a_object_name);
                     }
                     else
                     {
                      //new code
                          ...
                     }
       }

        int DBInterface.OldHandler(string object_type, string object_name)
        {
            object[] ParamValues = new object[2];
            ParamValues[0] = object_type;
            ParamValues[1] = object_name;

            return ExecuteNonQueryCommand("DeleteRuleFromAllPatterns", ParamValues);
        }