Proper way of using Marten for ASP.NET MVC/Core

Question

I just discovered Marten today and currently trying to learn on how to use this properly.

For creating new records, it can be as straight forward as providing a blank form/view then during submission - just open a new session then perform the saving like this:

using (var session = _documentStore.LightweightSession())
        {
            session.Store(model);
            session.SaveChanges();                
        }

But how about the updating existing records? After fetching the record and displaying it on the form, is it fine to just use the same code as I used above or is there another way? The only example I found for updating is loading the record from session by calling Load() method then editing the properties, after that is calling the SaveChanges() method of the session used.

Answer 1

Marten tracks documents using the document identity. The Id can be either a public field or property, and the name must be either id or Id or ID.

Quote from the doc:

Marten's .Net API makes no distinctions between inserts and updates. The Postgresql functions generated by Marten to update the document storage tables perform "upserts" for you. Anytime a document is registered through IDocumentSession.Store(document), Marten runs the "auto-assignment" policy for the id type of that document. See Document Identity for more information on document id's.

This means that you don't necessarily need to load a document before updating it. If you know its identity value, you could simply change some property on the document and call IDocumentSession.Store(document) which will perform an update if a document with this id already exists in the datastore.