Loading Documents by Id

var user = await session.LoadAsync<User>(id);              // Guid
var country = await session.LoadAsync<Country>("no");      // string
var invoice = await session.LoadAsync<Invoice>(42);        // int
var entry = await session.LoadAsync<Entry>(42L);           // long

A miss returns null.

Strong-typed ids

Both type parameters are explicit, which is what keeps this unambiguous against the four single-parameter overloads:

var order = await session.LoadAsync<Order, OrderId>(orderId);

Loading many

var users = await session.LoadManyAsync<User>(id1, id2, id3);
var users = await session.LoadManyAsync<User>(token, id1, id2, id3);
var orders = await session.LoadManyAsync<Order, OrderId>(ids, token);

The ids go into the statement as json_each(@ids) — where Marten writes = ANY($1) and Polecat uses OPENJSON — so one parameter carries any number of them.

TIP

Under a tracking session, LoadManyAsync preselects out of the identity map and asks only for the ids it does not hold. Reference identity would survive either way; what the preselect buys is the read itself.

Checking existence

if (await session.CheckExistsAsync<User>(id)) { … }

TIP

CheckExistsAsync routes through the LINQ path rather than a hand-written select 1 from … where id = ?. That is what makes it carry the tenant filter, the soft-delete filter and a hierarchy discriminator without restating any of them — it would otherwise be a fourth caller having to remember all three.

Loading raw JSON

var json = await session.LoadJsonAsync<User>(id);

The bytes are exactly what the serializer wrote. See Querying for Raw JSON.

Reading metadata

var meta = await session.MetadataForAsync<User>(id);

See Fisher Metadata.

What a load filters

A load applies the tenant and soft-delete filters, from the SQL itself rather than from the caller.

It does not apply a hierarchy discriminator, and that asymmetry is deliberate: a load names one row and the id is unique across the hierarchy, so a discriminator predicate would only turn "that id is a different sub-class" into the same answer as "no such id". A LoadAsync<TBase> returns whatever sub-class the row is; a LoadAsync<TDerived> narrows in memory, by testing what came back. See Document Hierarchies.