Selects only those keys that begin with the specified prefix. 
            
 Declaration Syntax
 Declaration Syntax| C# | 
public string Prefix { get; set; }
 Remarks
 Remarks
            Prefixes can be used to separate a bucket into different groupings of keys. 
            You can think of using prefix to make groups in the same way you'd use 
            a folder in a file system.) You can use prefix with delimiter to roll 
            up numerous objects into a single result under CommonPrefixes.