Undo an import of 5,000 contacts

Runs the sample. Generated for this page; it reads the connection string from the environment.

using ArxSamples.PostgreSql;
using ArxSamples.PostgreSql.Operations.Delete.RealCases;

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

await new RealCase2_CleanUpAnImport().RunAsync(new SampleContext(connectionString));

The sample, as it is in the repository.

using ARX.SDK.Services;
using static ArxSamples.PostgreSql.SampleOutput;

namespace ArxSamples.PostgreSql.Operations.Delete.RealCases;

/// <summary>
/// A contact import went wrong and must be undone, in two scenarios: all 5,000 imported contacts by their lead source in
/// one call; and the same call again, which finds nothing and says so with 0.
/// </summary>
public sealed class RealCase2_CleanUpAnImport : ISample
{
    public string Name => "delete-real-2-clean-up-an-import";

    public string Title => "Undo an import of 5,000 contacts";

    public async Task RunAsync(SampleContext dbContext)
    {
        var imported = Enumerable.Range(1, 5_000).Select(i =>
        {
            var contact = new ArxEntity("contact");
            contact["first_name"] = "Imported";
            contact["last_name"] = $"Row {i}";
            contact["email"] = $"bad-import-{i}@example.com";
            contact["lead_source"] = "Import 2026-11-08 (bad)";
            return contact;
        }).ToList();
        await dbContext.Service.CreateMultipleAsync(imported);

        await Scenario1_EveryImportedContactAsync(dbContext);

        await Scenario2_RunItAgainAsync(dbContext);
    }

    private static ArxEntity TheBadImport()
    {
        var match = new ArxEntity("contact");
        match["lead_source"] = "Import 2026-11-08 (bad)";
        return match;
    }

    /// <summary>1. The import tagged every row with its lead source: delete by that column. One statement.</summary>
    private static async Task Scenario1_EveryImportedContactAsync(SampleContext dbContext)
    {
        Step("1. Every contact of the bad import");

        var deleted = await dbContext.Service.DeleteAsync(TheBadImport(), new ArxDeleteOptions { Match = ArxMatch.Columns("lead_source") });
        Show($"{deleted} contacts deleted");

        /* ===========================================================
         * [DIRECT QUERY CHECK]
         * -----------------------------------------------------------
         * SELECT count(*)
         * FROM contact
         * WHERE lead_source = 'Import 2026-11-08 (bad)';
         * -- Expect: 0.
         * ===========================================================
         */
    }

    /// <summary>2. Running the clean-up again is safe: nothing matches, 0 deleted, no error.</summary>
    private static async Task Scenario2_RunItAgainAsync(SampleContext dbContext)
    {
        Step("2. Run the clean-up again");

        var deleted = await dbContext.Service.DeleteAsync(TheBadImport(), new ArxDeleteOptions { Match = ArxMatch.Columns("lead_source") });
        Show($"{deleted} deleted the second time");

        /* ===========================================================
         * [DIRECT QUERY CHECK]
         * -----------------------------------------------------------
         * SELECT count(*)
         * FROM contact
         * WHERE email LIKE 'bad-import-%';
         * -- Expect: 0.
         * ===========================================================
         */
    }
}

  > 1. Every contact of the bad import
      5000 contacts deleted
  > 2. Run the clean-up again
      0 deleted the second time