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How to store a c# List of objects into ElasticSearch with NEST 2.x

I'm developing a cross-platform app with xamarin.forms and I'm trying to look for a way to store a List of Objects directly into ElasticSearch so I can later search for results based on the objects of the lists. My scenario is the folloring:
public class Box {
[String(Index = FieldIndexOption.NotAnalyzed)]
public string id { get; set; }
public List<Category> categories { get; set; }
}
public class Category {
[String(Index = FieldIndexOption.NotAnalyzed)]
public string id { get; set; }
public string name { get; set; }
}
My aim is to be able to search for all the boxes that have a specific category.
I have tried to map everything properly like it says in the documentation but if I do it like that, when I store a box, it only stores the first category.
Is there actually a way to do it or is it just not possible with NEST?
Any tips are very welcome!
Thanks

It should just work fine with AutoMap using the code in the documentation:
If the index does not exist:
var descriptor = new CreateIndexDescriptor("indexyouwant")
.Mappings(ms => ms
.Map<Box>(m => m.AutoMap())
);
and then call something like:
await client.CreateIndexAsync(descriptor).ConfigureAwait(false);
or, when not using async:
client.CreateIndex(descriptor);
If the index already exists
Then forget about creating the CreateIndexDescriptor part above and just call:
await client.MapAsync<Box>(m => m.Index("existingindexname").AutoMap()).ConfigureAwait(false);
or, when not using async:
client.Map<Box>(m => m.Index("existingindexname").AutoMap());
Once you succesfully created a mapping for a type, you can index the documents.
Is it possible that you first had just one category in a box and mapped that to the index (Before you made it a List)? Because then you have to manually edit the mapping I guess, for example in Sense.
I don't know if you already have important data in your index but you could also delete the whole index (the mapping will be deleted too) and try it again. But then you'll lose all the documents you already indexed at the whole index.

Prevent EF default behaviour of saving duplicates via populated navigation properties

Imagine this pair of entities in Entity Framework:
public class Price
{
public virtual Document Document { get; set; }
public int DocumentId { get; set; }
//stuff
}
public class Document
{
public int DocumentId { get; set; }
//stuff
}
It's well known that if you populate the Document object in this pairing it can result in duplicates of existing objects, as explained here: Entityframework duplicating when calling savechanges - the solution is to only populate the key field before saving.
However, consider this situation in creating new objects.
Price price = repository.GetPriceById(1);
Document doc = new Document();
Right now that document has no Id, because the DocumentId field is an IDENTITY and it hasn't been sent to the database - it's just a virtual in-memory object. I can't get an Id for it unless I save it, and I don't want to do that at this point: the requirement is for a one-button save, not partial saves as the code works through. So, if I want to attach it to the Price object, I therefore have no way of making that association other than to assign it directly to the Document property. If I save it in that state, I'll get a duplicate.
So when I save it, I'm forced to do this:
repository.UpdatePrice(price.Document);
repository.SaveChanges();
price.DocumentId = price.Document.DocumentId;
price.Document = null;
repository.SaveChanges();
In which the set to null just seems ridiculous: there's no obvious reason for doing so and it feels like a future maintenance issue in waiting. All the more so because the one-click-save requirement means we have this problem all over the codebase. Is there any other way to deal with this issue?

Consecutive IDs in a navigation property List

I'm trying to make a discussion forum in ASP.NET MVC 5 (mostly as a test as I'm pretty new to C#/MVC/any coding).
I have two classes, Discussion and Message.
public class Discussion
{
public int DiscussionID { get; set; }
[Required]
[Display(Name="Discussion Title")]
public string DiscussionTitle { get; set; }
//[Required]
//ForumUser UserCreatedThread { get; set; }
[Required]
DateTime CreatedTime { get; set; }
public ICollection<Message> Messages { get; set; }
}
and
public class Message
{
public int MessageID { get; set; }
public int MessageNumber { get; set; }
[Required]
[Display(Name="Message Content")]
[DataType(DataType.MultilineText), AllowHtml]
public string Content { get; set; }
[Required]
public DateTime MessageTime { get; set; }
public virtual int DiscussionID { get; set; }
}
Discussion has a list of Messages which I would like the MessageID, or another property to be ordered 1,2,3,etc for each list. Currently if more than one discussion is created the MessageID can be 1,4,5,8,etc.
I started using a static method in the GetMessage() and GetDiscussion() methods to fix the IDs as the messages were returned to the controller by ordering the threads by the MessageID then iterating over them to change the values to 1,2,3,etc.
Now I've changed that to add a MessageNumber property, save the message to the database when a new message is created (using EF6), retrieve the message, get the count of messages, update MessageNumber to the count and save the changes.
The latter works but I assume could cause problems if a new message is created between saving the message then retrieving the count. Two messages would have the same MessageNumber.
Is there a better way to do this or a should I use a different way to access the messages that doesn't need the ID?

The id is just the key for the table; it's not really intended to be part of the UI, even though you commonly see ids floating around in URLs across the web. It's far better to expose and use something like a slug for user-facing scenarios.
Regardless, though, what you're trying to do is really not possible. The id is typically set as an identity column, and is auto-incremented for each row in the table. Even if you don't rely on auto-increment and set it manually, you still need to ensure a unique value for each one (i.e., you can't repeat id 1 for multiple rows. The only way around this would be to create a composite key utilizing a manually set id and something like the foreign key to the Discussions table, but that's really, really, not a good thing to do. Please, don't do that. Not only would any good DBA smack you for using a foreign key as part of a composite key for another table, but then you have a ton manual work to do each time you want to save a new message.
My best advice is to just not worry about the id. If you want a consecutive number, you can create another property much like the MessageNumber property you have already and put anything you want in that as long as it's not a key or index for the table. That means you can't (or at least shouldn't) actually retrieve anything using that field. You would still need to lookup by the actual row id, or something like a slug, as mentioned earlier.

I'm not sure why you want to do what you want to do, but if your implementation of Messages is a List, then you can use an index and add one to it. An indexes are by nature consecutive numbers. You would do that something like this:
int index = Messages.FindIndex(message => message.MessageID = theID);
If you want something a little more flexible:
Messages.Select((m, index) => new { index, Message = m })
.Single(message => message.MessageID == theID);

How to deal with C# object references in MongoDB?

I'm wondering how to handle when an object is used in multiple locations. Given th following code (just example code) :-
public class Group
{
public ObjectId Id { get; set; }
public string Name { get; set; }
public List<Person> People { get; set; }
public List<Meeting> Meetings { get; set; }
}
public class Meeting
{
public string Subject { get; set; }
public List<Person> Attendees { get; set; }
}
public class Person
{
public string Name { get; set; }
}
If I store the group as a mongodb document, it will serialize all the people and meetings. However the same Person object can be refered to in the People List and as an attendee of a meeting. However once serialized they become separate objects. How can I maintain that the same "Person" object is both in the People list and Meetings list?
Or is there are better way to model this? One thing that could be done is put the "People" in a separate Document and embeded / reference it? This then starts to create more and more separate collections, ideally I'd like to maintain references within a single document.
Or within a document should I Id each person and have one master list and then only store lists of Ids in the "Meetings" and use some kind of helper method to resolve the Id from the master list? Can be done, but a little bit ugly.

I'm not an expert with MongoDB but I think in this scenario each of these items should be a separate collection with references to get the results you are after.
Meetings have a Group ID and a list of Person ID attendees.
Groups have a list of Person ID members (people).
If a person can only belong to one group then they can have a single group ID.
Once they go into the database the only option you have with your existing design is checking for name equality which as you say can be done but doesn't seem like the right approach.
Essentially you are using the embedded relationship model with how you are storing 'Person' in 'Group' and 'Meeting' but if you want the same 'Person' object for both then you need to use references for Attendees or both. This seems like the simplest approach to me while not 'fighting' against the standard behaviour.

History tables in .NET MVC code first approach?

I need to track a change history of some database objects in a MVC .NET application using the code first approach.
Here is what is meant by history table:
http://database-programmer.blogspot.de/2008/07/history-tables.html
I would use a history table for it, if I would write the SQL queries myself. But in the code first approach the SQL is generated... and I would like to stick to this paradigm.
The goal is a structure that holds all "old" revisions of changed/deleted entries together with some additional information (e.g. timestamp, user who changed it, ...)
Any ideas?
Regards,
Stefan
To be more specific - here is some code example:
public class Node {
public int NodeID { get; set; }
public string? data { get; set; } // sample data
}
public class NodeHistory {
public int NodeID { get; set; }
public string? data { get; set; }
public int UserID { get; set; }
public DataTime timestamp { get; set; }
}
What I need is some "framework" assistance to be able to add an entry to NodeHistory whenever a change is -persisted- to table the Node structure.
That means: Just overriding the set-method isn't a solution, as it would also create an entry, if the change to a "Node" is not persisted at the end (e.g. roleback).

I think the best approach for me would be to use a repository pattern and do the insertion into the NodeHistory table on every operation on the Node object that you see fit to keep a history of.
EDIT: Some code
public class NodeRepository{
public Node EditNode(Node toEdit, int userId){
using(new TransactionScope())
{
//Edit Node in NodeContext like you would anyway without repository
NodeContext.NodeHistories.Add(new NodeHistory(){//initialise NodeHistory stuff here)
NodeContext.SaveChagnes();
}
}
}
public class NodeContext:DbContext{
public DbSet<Node> Nodes{get;set;}
public DbSet<NodeHistory> NodeHistories{get;set;}
}
If you are looking for something simpler than this, then I have no idea what it might be.

This is really something you should do with a trigger. Yes, you have to write some sql for it, but then history is updated no matter how the update occurs, either manually, or through some other means.