Controller query paging

Return an IQueryable

For a default Arc-wrapped MVC GET, return an unmaterialized database query. This alternative banking declaration uses the shared domain concepts, an ASP.NET Core Arc host, configured authorization, and the MongoDB provider:

using System.Linq;
using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Mvc;
using MongoDB.Driver;
using MongoDB.Driver.Linq;

namespace Banking.Accounts;

public record DebitAccount(AccountId Id, AccountName Name, decimal Balance);

[Authorize(Roles = "AccountReader")]
[Route("api/accounts")]
public class AccountsController(IMongoCollection<DebitAccount> collection) : ControllerBase
{
    [HttpGet]
    public IQueryable<DebitAccount> AllAccounts() =>
        collection.AsQueryable().OrderBy(account => account.Id);

    [HttpGet("positive")]
    public IQueryable<DebitAccount> PositiveAccounts() =>
        collection.AsQueryable().Where(account => account.Balance > 0)
            .OrderBy(account => account.Id);
}

GET /api/accounts?page=0&pageSize=25
GET /api/accounts/positive?page=1&pageSize=10&sortby=name&sortDirection=asc

The action filter establishes the paging/sorting context. QueryableQueryRenderer counts the filtered query, applies requested sorting, then applies Skip/Take. A database-backed LINQ provider can perform this work server-side; an in-memory queryable cannot undo earlier materialization.

Paging contract

page is zero-based, pageSize is the requested size, and sortby/sortDirection select the sort. Use positive, bounded sizes and a stable ordering. Client-requested ordering replaces the method’s primary ordering; account for duplicate sort values in production.

The response paging object has page, size, totalItems, totalPages. See query result metadata. Without a paging request, the query is not automatically capped.

Lists, arrays, and plain enumerable results are not automatically sliced. A manually paged list does not automatically carry the database’s total count. Do not return a QueryResult from a wrapped action to fix that: it becomes nested data, not outer metadata.

Manual control

IQueryContextManager.Current exposes Paging and Sorting if an integration needs them. When using MongoDB’s fluent API, compose Skip, Limit, and Sort before execution; use expression sorting or a SortDefinition, not SortBy(string).

For a completely custom response/metadata contract, use [AspNetResult] and supply the full MVC response yourself. That is an opt-out from Arc wrapping and needs a matching client. Prefer the queryable path unless you need that control.

Observable paging

A stream does not become paged merely because it emits a collection. Arc’s MongoDB Observe() supplies provider-aware paging; arbitrary subjects must implement it themselves. See controller observable queries.