[Question] Client .Net Nest with attachment highlight feature

Hello everyone,

I started recently using ES, with its .net client NEST.
A lot of questions to ask.

I'm currently blocked while trying to highlight search results in attachment field.
The indexation works well, the mapping seems correct, the encode and decode work well too,

Once I tried to search by keyword, EA seems to be able to find the right documents which contain the keyword, but in the highlight result, instead of showing the decoded text, it shows nothing, or the encoded one.

Read from another post treating some same features, the solution is to set store = yes.

So I tried to configure it in my C# class file with
[ElasticProperty(Name = "attach", Type = FieldType.Attachment, Store=true, TermVector = TermVectorOption.WithPositionsOffsets)]
public string attach { get; set; }

and the query is the follwing
{
"fields" : ["name","attach"],
"query" : {
"query_string" : {
"query" : "settings"
}
},
"highlight" : {
"fields" : {
"attach" : {}
}
}
}

Do you have some idea?
Thanks

Another thing that I found while using EA is the encode file,
In fact, in the official "Attachment in Action" post,
http://www.elasticsearch.cn/tutorials/2011/07/18/attachment-type-in-action.html
first of all, it's under linux environment, and the commands used for encoding files depend on some perl scripts. Finally, the contain of the result encoded file seems to be different under a windows system and a linux system.
Since I use .net framwork, the function that i used for encoding it's from c# api, convert.tobase64string.

Thank you very much!