Read many records

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.RetrieveMultiple.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_RetrieveManyRecords().RunAsync(dbContext);

The sample, as it is in the repository.

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

using static ArxSamples.MongoDb.SampleOutput;

namespace ArxSamples.MongoDb.Operations.RetrieveMultiple.Basics;

/// <summary>
/// Read many documents with conditions and an order, in three scenarios: comparisons and an order, text patterns, and
/// what null means on MongoDB.
/// </summary>
/// <remarks>
/// Contains, BeginsWith and EndsWith ignore case, and their text is never read as a regular expression. <c>Null</c>
/// matches a stored null and a missing field; NotEqual and the other negations never match either, as in SQL.
/// </remarks>
public sealed class Basic1_RetrieveManyRecords : ISample
{
    public string Name => "retrieve-multiple-basics-1-retrieve-many-records";

    public string Title => "Read many records";

    public async Task RunAsync(SampleContext dbContext)
    {
        var contacts = new List<ArxEntity>();

        foreach (var (first, last, score) in new[] { ("Ana", "Silva", (int?)80), ("Bruno", "Costa", 55), ("Carla", "Sá", null), ("Diogo", "Silva (Jr.)", 91) })
        {
            var contact = new ArxEntity("contact");
            contact["first_name"] = first;
            contact["last_name"] = last;
            contact["segment"] = "M96";

            if (score != null)
            {
                contact["score"] = score;
            }

            contacts.Add(contact);
        }

        await dbContext.Service.CreateMultipleAsync(contacts);

        await Scenario1_ComparisonsAndAnOrderAsync(dbContext.Service);

        await Scenario2_TextPatternsAsync(dbContext.Service);

        await Scenario3_WhatNullMeansAsync(dbContext.Service);
    }

    private static ArxQueryExpression Segment()
    {
        var query = new ArxQueryExpression("contact");
        query.ColumnSet.AddColumns("first_name", "last_name", "score");
        query.Criteria.AddCondition("segment", ArxConditionOperator.Equal, "M96");
        return query;
    }

    /// <summary>1. A score of 60 or more, best first.</summary>
    private static async Task Scenario1_ComparisonsAndAnOrderAsync(ArxMongoDbService service)
    {
        Step("1. Comparisons and an order");

        var query = Segment();
        query.Criteria.AddCondition("score", ArxConditionOperator.GreaterEqual, 60);
        query.AddOrder("score", ArxOrderType.Descending);

        var page = await service.RetrieveMultipleAsync(query);

        Show(string.Join(", ", page.Entities.Select(x => $"{x["first_name"]} {x["score"]}")));

        /* ===========================================================
         * [DIRECT QUERY CHECK]
         * -----------------------------------------------------------
         * db.contact.find({ segment: "M96", score: { $gte: 60 } }, { first_name: 1, score: 1 }).sort({ score: -1 })
         * -- Expect: 2 documents: Diogo 91, Ana 80.
         * ===========================================================
         */
    }

    /// <summary>2. Last names containing "silva", any case; "(Jr.)" is plain text, not a pattern.</summary>
    private static async Task Scenario2_TextPatternsAsync(ArxMongoDbService service)
    {
        Step("2. Text patterns");

        var silva = Segment();
        silva.Criteria.AddCondition("last_name", ArxConditionOperator.Contains, "silva");

        var junior = Segment();
        junior.Criteria.AddCondition("last_name", ArxConditionOperator.EndsWith, "(Jr.)");

        Show($"contains silva: {(await service.RetrieveMultipleAsync(silva)).Entities.Count}; ends with (Jr.): {(await service.RetrieveMultipleAsync(junior)).Entities.Count}");

        /* ===========================================================
         * [DIRECT QUERY CHECK]
         * -----------------------------------------------------------
         * db.contact.countDocuments({ segment: "M96", last_name: /silva/i })
         * -- Expect: 2.
         * ===========================================================
         */
    }

    /// <summary>3. Carla has no score: Null finds her; NotEqual 80 doesn't.</summary>
    private static async Task Scenario3_WhatNullMeansAsync(ArxMongoDbService service)
    {
        Step("3. What null means");

        var noScore = Segment();
        noScore.Criteria.AddCondition("score", ArxConditionOperator.Null);

        var notEighty = Segment();
        notEighty.Criteria.AddCondition("score", ArxConditionOperator.NotEqual, 80);

        Show($"no score: {string.Join(", ", (await service.RetrieveMultipleAsync(noScore)).Entities.Select(x => x["first_name"]))}; "
            + $"score not 80: {string.Join(", ", (await service.RetrieveMultipleAsync(notEighty)).Entities.Select(x => x["first_name"]))}");

        /* ===========================================================
         * [DIRECT QUERY CHECK]
         * -----------------------------------------------------------
         * db.contact.find({ segment: "M96", score: null }, { first_name: 1 })
         * -- Expect: 1 document, Carla (her document has no score field).
         * ===========================================================
         */
    }
}

  > 1. Comparisons and an order
      Diogo 91, Ana 80
  > 2. Text patterns
      contains silva: 2; ends with (Jr.): 1
  > 3. What null means
      no score: Carla; score not 80: Bruno, Diogo