A string that represents the name of an index field. 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:
 Declaration Syntax
 Declaration Syntax| C# | 
public string IndexFieldName { get; set; }