Read one record

Runs the sample. Generated for this page; it reads the connection string from the environment and first remakes the sample database from sample-schema.json.

using ArxSamples.MongoDb;
using ArxSamples.MongoDb.Operations.Retrieve.Basics;

// The connection string comes from the environment, never from the code (see "Configure the connection").
var connectionString = Environment.GetEnvironmentVariable("ARX_SAMPLES_MONGODB")
    ?? throw new InvalidOperationException("Set the ARX_SAMPLES_MONGODB environment variable to your MongoDB connection string.");

var dbContext = new SampleContext(connectionString);

// Every run starts from the sample data: this deletes and makes again what sample-schema.json lists
// (save the file in the project folder, see Get started).
await dbContext.Direct.ResetAsync();

await new Basic1_RetrieveOneRecord().RunAsync(dbContext);

The sample, as it is in the repository.

using ARX.SDK.MongoDb.Services;
using ARX.SDK.Services;

using static ArxSamples.MongoDb.SampleOutput;

namespace ArxSamples.MongoDb.Operations.Retrieve.Basics;

/// <summary>
/// Read one document, in three scenarios: by its id with every field, with chosen fields, and by a key; an id no
/// document has reads null.
/// </summary>
/// <remarks>The id comes back under the declared column's name (<c>account_id</c>) and as <see cref="ArxEntity.RecordId"/>.</remarks>
public sealed class Basic1_RetrieveOneRecord : ISample
{
    public string Name => "retrieve-basics-1-retrieve-one-record";

    public string Title => "Read one record";

    public async Task RunAsync(SampleContext dbContext)
    {
        var account = new ArxEntity("account");
        account["name"] = "Consolidated Messenger";
        account["account_number"] = "ACC-M951";
        account["employee_count"] = 75;
        var id = await dbContext.Service.CreateAsync(account);

        await Scenario1_ByIdAsync(dbContext.Service, id);

        await Scenario2_ChosenFieldsAsync(dbContext.Service, id);

        await Scenario3_ByAKeyAsync(dbContext.Service);
    }

    /// <summary>1. By the id Create returned: every field.</summary>
    private static async Task Scenario1_ByIdAsync(ArxMongoDbService service, ArxRecordId id)
    {
        Step("1. By id");

        ArxEntity? account = await service.RetrieveAsync("account", id);

        Show($"{account?["name"]}, {account?["employee_count"]} employees, id {account?["account_id"]}");

        /* ===========================================================
         * [DIRECT QUERY CHECK]
         * -----------------------------------------------------------
         * db.account.find({ account_number: "ACC-M951" })
         * -- Expect: 1 document, Consolidated Messenger, employee_count 75.
         * ===========================================================
         */
    }

    /// <summary>2. Only the fields you name (the id always comes too).</summary>
    private static async Task Scenario2_ChosenFieldsAsync(ArxMongoDbService service, ArxRecordId id)
    {
        Step("2. Chosen fields");

        ArxEntity? account = await service.RetrieveAsync("account", id, new ArxColumnSet("name"));

        Show($"fields read: {string.Join(", ", account!.Attributes.Keys)}");

        /* ===========================================================
         * [DIRECT QUERY CHECK]
         * -----------------------------------------------------------
         * db.account.find({ account_number: "ACC-M951" }, { name: 1 })
         * -- Expect: 1 document, _id and name.
         * ===========================================================
         */
    }

    /// <summary>3. By the account number (a declared key), and a number no account has: null.</summary>
    private static async Task Scenario3_ByAKeyAsync(ArxMongoDbService service)
    {
        Step("3. By a key");

        var match = new ArxEntity("account");
        match["account_number"] = "ACC-M951";
        ArxEntity? found = await service.RetrieveAsync(match, new ArxRetrieveOptions { Match = ArxMatch.Key("account_number") });

        match["account_number"] = "ACC-M959";
        ArxEntity? missing = await service.RetrieveAsync(match, new ArxRetrieveOptions { Match = ArxMatch.Key("account_number") });

        Show($"ACC-M951: {found?["name"]}; ACC-M959: {(missing == null ? "null" : "found")}");

        /* ===========================================================
         * [DIRECT QUERY CHECK]
         * -----------------------------------------------------------
         * db.account.countDocuments({ account_number: "ACC-M959" })
         * -- Expect: 0.
         * ===========================================================
         */
    }
}

  > 1. By id
      Consolidated Messenger, 75 employees, id 6af534034d10bda79422b8d8
  > 2. Chosen fields
      fields read: account_id, name
  > 3. By a key
      ACC-M951: Consolidated Messenger; ACC-M959: null