AWS SDK for .NET Documentation
IndexFieldName Property
AmazonAmazon.CloudSearch_2011_02_01.ModelIndexFieldIndexFieldName Did this page help you?   Yes   No    Tell us about it...
The name of a field in the search index. Field names must begin with a letter and can contain the following characters: a-z (lowercase), 0-9, and _ (underscore). Uppercase letters and hyphens are not allowed. The names "body", "docid", and "text_relevance" are reserved and cannot be specified as field or rank expression names.

Constraints:

Length
1 - 64
Pattern
[a-z][a-z0-9_]*

Declaration Syntax
C#
public string IndexFieldName { get; set; }

Assembly: AWSSDK (Module: AWSSDK) Version: 1.5.60.0 (1.5.60.0)