internal void AddField(string fieldName, int elementIndex)
        {
            var map = new MapField(fieldName, elementIndex);

            MapFields.Add(map);
        }
        internal void AddField(string fieldName, int start, int length, string startWith = "", string columnName = "")
        {
            var map = new MapField(fieldName, start, length, startWith, columnName);

            this.MapFields.Add(map);
        }