public FieldSchemaMetadata MetadataFor(string fieldName)
        {
            FieldSchemaMetadata field;

            lock (_lock)
            {
                field = _fields.SingleOrDefault(_ => _.Name.EqualsIgnoreCase(fieldName));
                if (field == null)
                {
                    field = new FieldSchemaMetadata {
                        Name = fieldName
                    };
                    _fields.Add(field);
                }
            }

            return(field);
        }
 public void AddField(FieldSchemaMetadata field)
 {
     _fields.Add(field);
 }