MySQL · RetrieveMultiple
Read other row sources: a view in a schema, a summary view, a table with no id
RetrieveMultiple reads more than tables: whatever name the query is given, MySQL resolves it, so a view, a view in another schema or a table without an id is read with the same ArxQueryExpression: criteria, links, order, paging, aggregates. Three scenarios (functions are Advanced8):
- A view in another database, MySQL's schema (
arx_samples_reporting.vw_product_catalogue), linked to a table and aggregated. - A summary view: it runs its query at each read, so a new order shows at once.
- A table with no id (
web_visit), read with a date range and a link.
MySQL has no materialized views and no inheritance; a partitioned table is read like any table: partitions are invisible to statements.
Set up for this page
Besides the sample itself, it uses SampleContext.cs (the dbContext every sample is given); SampleOutput.cs (Step and Show, which print); SampleContext.Application.cs (dbContext.Service, the application's ARX service); SampleCatalog.cs (the tables' ids, keys, lookups and display names), in the files below.
Before scenario 1 the sample runs this, so the service and the rows the scenarios use are there:
var accounts = new Dictionary<string, ArxRecordId>();
foreach (var (number, name) in new[] { ("ACC-R781", "Summit Supplies"), ("ACC-R782", "Harbor Hardware") })
{
var account = new ArxEntity("account");
account["name"] = name;
account["account_number"] = number;
accounts[number] = await service.CreateAsync(account);
}
var category = new ArxEntity("product_category");
category["name"] = "Tools R78";
var categoryId = await service.CreateAsync(category);
var products = new Dictionary<string, ArxRecordId>();
foreach (var (sku, name, price, active) in new[] { ("SKU-R781", "Hammer", 25m, true), ("SKU-R782", "Saw", 40m, true), ("SKU-R783", "Old drill", 90m, false) })
{
var product = new ArxEntity("product");
product["sku"] = sku;
product["name"] = name;
product["category_id"] = new ArxEntityReference("product_category", categoryId);
product["unit_price"] = price;
product["is_active"] = active;
products[sku] = await service.CreateAsync(product);
}
foreach (var (orderNumber, account, total, lines) in new[]
{
("SO-R781", "ACC-R781", 180m, new[] { ("SKU-R781", 4, 25m), ("SKU-R782", 2, 40m) }),
("SO-R782", "ACC-R781", 200m, Array.Empty<(string, int, decimal)>()),
("SO-R783", "ACC-R782", 115m, new[] { ("SKU-R781", 1, 25m), ("SKU-R783", 1, 90m) }),
})
{
var order = new ArxEntity("sales_order");
order["order_number"] = orderNumber;
order["account_id"] = new ArxEntityReference("account", accounts[account]);
order["ordered_on"] = new DateTime(2026, 11, 8, 9, 0, 0, DateTimeKind.Utc);
order["total"] = total;
var orderId = await service.CreateAsync(order);
foreach (var (sku, quantity, price) in lines)
{
var line = new ArxEntity("order_line");
line["order_id"] = new ArxEntityReference("sales_order", orderId);
line["product_id"] = new ArxEntityReference("product", products[sku]);
line["quantity"] = quantity;
line["unit_price"] = price;
await service.CreateAsync(line);
}
}1 A view in another schema, linked to a table and aggregated
arx_samples_reporting.vw_product_catalogue (active products with their category's name), named with its schema, then used like any table: a criterion, a LEFT link to order_line (a table), units sold per product, the best seller first. The inactive Old drill isn't in the view, so it isn't in the result.
Already in scope: service (ArxMySqlDbService)
var query = new ArxQueryExpression("arx_samples_reporting.vw_product_catalogue") { AggregateInfo = new ArxAggregateInfo() };
query.ColumnSet.AddColumns("sku", "name");
query.Criteria.AddCondition("category", ArxConditionOperator.Equal, "Tools R78");
query.LinkEntities.Add(new ArxLinkEntity("order_line", "id", "product_id", ArxJoinOperator.Left) { EntityAlias = "l" });
query.AggregateInfo.AddAggregateColumn("units", "l.quantity", ArxAggregateOperator.Sum);
query.AggregateInfo.AddGroupByColumns("sku", "name");
query.AddOrder("units", ArxOrderType.Descending);
var rows = await service.RetrieveMultipleAsync(query);
foreach (var row in rows.Entities)
{
Console.WriteLine($"{row["sku"]} {row["name"],-6} {row["units"]} sold (entity name: {row.EntityName})");
}Check it in the database
Run it in any SQL tool connected to the database, after the code has run.
SELECT v.sku, v.name, sum(l.quantity) AS units
FROM arx_samples_reporting.vw_product_catalogue v
LEFT JOIN order_line l ON l.product_id = v.id
WHERE v.category = 'Tools R78'
GROUP BY v.sku, v.name
ORDER BY units DESC;Expect: 2 rows: SKU-R781 Hammer 5, SKU-R782 Saw 2 (no Old drill: inactive).
2 A summary view: always up to date
vw_account_sales_summary (orders and revenue per account) runs its query at each read: an order created afterwards shows in the next read at once.
Already in scope: service (ArxMySqlDbService), harbor (ArxRecordId)
foreach (var row in (await service.RetrieveMultipleAsync(SalesSummary())).Entities)
{
Console.WriteLine($"{row["name"],-15} orders {row["orders"]}, revenue {row["revenue"]:N2}");
}
var order = new ArxEntity("sales_order");
order["order_number"] = "SO-R784";
order["account_id"] = new ArxEntityReference("account", harbor);
order["ordered_on"] = new DateTime(2026, 11, 8, 15, 0, 0, DateTimeKind.Utc);
order["total"] = 500m;
await service.CreateAsync(order);
var snapshot = (await service.RetrieveMultipleAsync(SalesSummary())).Entities.Single(x => (string)x["name"]! == "Harbor Hardware");
var live = new ArxQueryExpression("sales_order") { AggregateInfo = new ArxAggregateInfo() };
live.Criteria.AddCondition("account_id", ArxConditionOperator.Equal, harbor.AsInt64());
live.AggregateInfo.AddAggregateColumn("orders", "id", ArxAggregateOperator.Count);
live.AggregateInfo.AddAggregateColumn("revenue", "total", ArxAggregateOperator.Sum);
var now = (await service.RetrieveMultipleAsync(live)).Entities[0];
Console.WriteLine($"a new order for Harbor: the view says {snapshot["orders"]} orders, {snapshot["revenue"]:N2}; the tables say {now["orders"]} orders, {now["revenue"]:N2}");Defined once in this sample.
private static ArxQueryExpression SalesSummary()
{
var query = new ArxQueryExpression("vw_account_sales_summary");
query.ColumnSet.AddColumns("name", "orders", "revenue");
query.Criteria.AddCondition("account_number", ArxConditionOperator.BeginsWith, "ACC-R78");
query.AddOrder("revenue", ArxOrderType.Descending);
return query;
}Check it in the database
Run it in any SQL tool connected to the database, after the code has run.
SELECT name, orders, revenue
FROM vw_account_sales_summary
WHERE account_number LIKE 'ACC-R78%'
ORDER BY revenue DESC;Expect: Harbor Hardware 2 615.00, Summit Supplies 2 380.00 (the view is always current). SELECT COUNT(*), SUM(total) FROM sales_order WHERE order_number IN ('SO-R783', 'SO-R784'); 2, 615.00: Harbor's orders now.
3 A table with no id, read with a date range and a link
web_visit has no id (declared NoIdColumn): its rows are created together and read with a date range and a link to the account.
Already in scope: service (ArxMySqlDbService), accounts (Dictionary<string, ArxRecordId>)
var visits = new[]
{
("ACC-R781", "/pricing", new DateOnly(2026, 3, 10)),
("ACC-R781", "/pricing", new DateOnly(2026, 8, 2)),
("ACC-R781", "/contact", new DateOnly(2026, 9, 15)),
("ACC-R782", "/pricing", new DateOnly(2026, 10, 1)),
}.Select(x =>
{
var visit = new ArxEntity("web_visit");
visit["account_id"] = new ArxEntityReference("account", accounts[x.Item1]);
visit["page"] = x.Item2;
visit["visited_on"] = x.Item3;
return visit;
}).ToList();
await service.CreateMultipleAsync(visits);
var query = new ArxQueryExpression("web_visit");
query.ColumnSet.AddColumns("page", "visited_on");
query.Criteria.AddCondition("visited_on", ArxConditionOperator.GreaterEqual, new DateOnly(2026, 7, 1));
query.Criteria.AddCondition("visited_on", ArxConditionOperator.LessThan, new DateOnly(2026, 10, 1));
var account = query.AddLink("account", "account_id", "id", ArxJoinOperator.Inner);
account.EntityAlias = "acc";
account.ColumnSet.AddColumn("name");
account.LinkCriteria.AddCondition("account_number", ArxConditionOperator.BeginsWith, "ACC-R78");
query.AddOrder("visited_on", ArxOrderType.Ascending);
foreach (var row in (await service.RetrieveMultipleAsync(query)).Entities)
{
Console.WriteLine($"July to September: {row["visited_on"]:yyyy-MM-dd} {row["page"],-9} {row["acc.name"]}");
}Check it in the database
Run it in any SQL tool connected to the database, after the code has run.
SELECT v.visited_on, v.page, a.name
FROM web_visit v
JOIN account a ON a.id = v.account_id AND a.account_number LIKE 'ACC-R78%'
WHERE v.visited_on >= '2026-07-01' AND v.visited_on < '2026-10-01'
ORDER BY v.visited_on;Expect: 2 rows: 2026-08-02 /pricing, 2026-09-15 /contact (both Summit Supplies).
Run the complete sample
The code above comes from one program, built in a fresh project and run against the database. To run it yourself, here is every file and step.
The program, its files and how to run it
Run it locally
- .NET SDK: .NET SDK 10.0.100 or later 10.0.x (target
net10.0). - Create the project:
Terminal dotnet new console -n ArxSample -f net10.0 cd ArxSample - Install the packages:
Terminal dotnet add package ARX.SDK.MySQL --version 1.0.0-rc.1 - Database: a MySQL 8.4 (tested with 8.4.13) database with the sample schema.
- Configuration: set
ARX_SAMPLES_MYSQLto its connection string. Nothing is hard-coded. - Source code: replace
Program.csand add the 5 other files below, with the file names shown. - Run it:
Terminal dotnet run - Expected output: below.
The files
Runs the sample. Generated for this page; it reads the connection string from the environment.
using ArxSamples.MySQL;
using ArxSamples.MySQL.Operations.RetrieveMultiple.AdvancedCases;
// The connection string comes from the environment, never from the code (see "Configure the connection").
var connectionString = Environment.GetEnvironmentVariable("ARX_SAMPLES_MYSQL")
?? throw new InvalidOperationException("Set the ARX_SAMPLES_MYSQL environment variable to your MySQL connection string.");
await new Advanced7_ReadOtherRowSources().RunAsync(new SampleContext(connectionString));
The sample, as it is in the repository.
using ARX.SDK.Query;
using ARX.SDK.Services;
using static ArxSamples.MySQL.SampleOutput;
namespace ArxSamples.MySQL.Operations.RetrieveMultiple.AdvancedCases;
/// <summary>
/// RetrieveMultiple reads more than tables: whatever name the query is given, MySQL resolves it, so a view, a view
/// in another schema or a table without an id is read with the same <see cref="ArxQueryExpression"/>: criteria, links,
/// order, paging, aggregates. Three scenarios (functions are <c>Advanced8</c>):
/// <list type="number">
/// <item>A view in another database, MySQL's schema (<c>arx_samples_reporting.vw_product_catalogue</c>), linked to a table and aggregated.</item>
/// <item>A summary view: it runs its query at each read, so a new order shows at once.</item>
/// <item>A table with no id (<c>web_visit</c>), read with a date range and a link.</item>
/// </list>
/// MySQL has no materialized views and no inheritance; a partitioned table is read like any table: partitions are
/// invisible to statements.
/// </summary>
public sealed class Advanced7_ReadOtherRowSources : ISample
{
public string Name => "retrieve-multiple-advanced-7-read-other-row-sources";
public string Title => "Read other row sources: a view in a schema, a summary view, a table with no id";
public async Task RunAsync(SampleContext dbContext)
{
var accounts = new Dictionary<string, ArxRecordId>();
foreach (var (number, name) in new[] { ("ACC-R781", "Summit Supplies"), ("ACC-R782", "Harbor Hardware") })
{
var account = new ArxEntity("account");
account["name"] = name;
account["account_number"] = number;
accounts[number] = await dbContext.Service.CreateAsync(account);
}
var category = new ArxEntity("product_category");
category["name"] = "Tools R78";
var categoryId = await dbContext.Service.CreateAsync(category);
var products = new Dictionary<string, ArxRecordId>();
foreach (var (sku, name, price, active) in new[] { ("SKU-R781", "Hammer", 25m, true), ("SKU-R782", "Saw", 40m, true), ("SKU-R783", "Old drill", 90m, false) })
{
var product = new ArxEntity("product");
product["sku"] = sku;
product["name"] = name;
product["category_id"] = new ArxEntityReference("product_category", categoryId);
product["unit_price"] = price;
product["is_active"] = active;
products[sku] = await dbContext.Service.CreateAsync(product);
}
foreach (var (orderNumber, account, total, lines) in new[]
{
("SO-R781", "ACC-R781", 180m, new[] { ("SKU-R781", 4, 25m), ("SKU-R782", 2, 40m) }),
("SO-R782", "ACC-R781", 200m, Array.Empty<(string, int, decimal)>()),
("SO-R783", "ACC-R782", 115m, new[] { ("SKU-R781", 1, 25m), ("SKU-R783", 1, 90m) }),
})
{
var order = new ArxEntity("sales_order");
order["order_number"] = orderNumber;
order["account_id"] = new ArxEntityReference("account", accounts[account]);
order["ordered_on"] = new DateTime(2026, 11, 8, 9, 0, 0, DateTimeKind.Utc);
order["total"] = total;
var orderId = await dbContext.Service.CreateAsync(order);
foreach (var (sku, quantity, price) in lines)
{
var line = new ArxEntity("order_line");
line["order_id"] = new ArxEntityReference("sales_order", orderId);
line["product_id"] = new ArxEntityReference("product", products[sku]);
line["quantity"] = quantity;
line["unit_price"] = price;
await dbContext.Service.CreateAsync(line);
}
}
await Scenario1_AViewInAnotherSchemaAsync(dbContext);
await Scenario2_ASummaryViewAsync(dbContext, accounts["ACC-R782"]);
await Scenario3_ATableWithNoIdAsync(dbContext, accounts);
}
/// <summary>
/// 1. <c>arx_samples_reporting.vw_product_catalogue</c> (active products with their category's name), named with its schema, then
/// used like any table: a criterion, a LEFT link to <c>order_line</c> (a table), units sold per product, the best
/// seller first. The inactive Old drill isn't in the view, so it isn't in the result.
/// </summary>
private static async Task Scenario1_AViewInAnotherSchemaAsync(SampleContext dbContext)
{
Step("1. A view in another schema, linked to a table and aggregated");
var query = new ArxQueryExpression("arx_samples_reporting.vw_product_catalogue") { AggregateInfo = new ArxAggregateInfo() };
query.ColumnSet.AddColumns("sku", "name");
query.Criteria.AddCondition("category", ArxConditionOperator.Equal, "Tools R78");
query.LinkEntities.Add(new ArxLinkEntity("order_line", "id", "product_id", ArxJoinOperator.Left) { EntityAlias = "l" });
query.AggregateInfo.AddAggregateColumn("units", "l.quantity", ArxAggregateOperator.Sum);
query.AggregateInfo.AddGroupByColumns("sku", "name");
query.AddOrder("units", ArxOrderType.Descending);
var rows = await dbContext.Service.RetrieveMultipleAsync(query);
foreach (var row in rows.Entities)
{
Show($"{row["sku"]} {row["name"],-6} {row["units"]} sold (entity name: {row.EntityName})");
}
/* ===========================================================
* [DIRECT QUERY CHECK]
* -----------------------------------------------------------
* SELECT v.sku, v.name, sum(l.quantity) AS units
* FROM arx_samples_reporting.vw_product_catalogue v
* LEFT JOIN order_line l ON l.product_id = v.id
* WHERE v.category = 'Tools R78'
* GROUP BY v.sku, v.name
* ORDER BY units DESC;
* -- Expect: 2 rows: SKU-R781 Hammer 5, SKU-R782 Saw 2 (no Old drill: inactive).
* ===========================================================
*/
}
private static ArxQueryExpression SalesSummary()
{
var query = new ArxQueryExpression("vw_account_sales_summary");
query.ColumnSet.AddColumns("name", "orders", "revenue");
query.Criteria.AddCondition("account_number", ArxConditionOperator.BeginsWith, "ACC-R78");
query.AddOrder("revenue", ArxOrderType.Descending);
return query;
}
/// <summary>
/// 2. <c>vw_account_sales_summary</c> (orders and revenue per account) runs its query at each read: an order created
/// afterwards shows in the next read at once.
/// </summary>
private static async Task Scenario2_ASummaryViewAsync(SampleContext dbContext, ArxRecordId harbor)
{
Step("2. A summary view: always up to date");
foreach (var row in (await dbContext.Service.RetrieveMultipleAsync(SalesSummary())).Entities)
{
Show($"{row["name"],-15} orders {row["orders"]}, revenue {row["revenue"]:N2}");
}
var order = new ArxEntity("sales_order");
order["order_number"] = "SO-R784";
order["account_id"] = new ArxEntityReference("account", harbor);
order["ordered_on"] = new DateTime(2026, 11, 8, 15, 0, 0, DateTimeKind.Utc);
order["total"] = 500m;
await dbContext.Service.CreateAsync(order);
var snapshot = (await dbContext.Service.RetrieveMultipleAsync(SalesSummary())).Entities.Single(x => (string)x["name"]! == "Harbor Hardware");
var live = new ArxQueryExpression("sales_order") { AggregateInfo = new ArxAggregateInfo() };
live.Criteria.AddCondition("account_id", ArxConditionOperator.Equal, harbor.AsInt64());
live.AggregateInfo.AddAggregateColumn("orders", "id", ArxAggregateOperator.Count);
live.AggregateInfo.AddAggregateColumn("revenue", "total", ArxAggregateOperator.Sum);
var now = (await dbContext.Service.RetrieveMultipleAsync(live)).Entities[0];
Show($"a new order for Harbor: the view says {snapshot["orders"]} orders, {snapshot["revenue"]:N2}; the tables say {now["orders"]} orders, {now["revenue"]:N2}");
/* ===========================================================
* [DIRECT QUERY CHECK]
* -----------------------------------------------------------
* SELECT name, orders, revenue
* FROM vw_account_sales_summary
* WHERE account_number LIKE 'ACC-R78%'
* ORDER BY revenue DESC;
* -- Expect: Harbor Hardware 2 615.00, Summit Supplies 2 380.00 (the view is always current).
* SELECT COUNT(*), SUM(total)
* FROM sales_order
* WHERE order_number IN ('SO-R783', 'SO-R784');
* -- Expect: 2, 615.00: Harbor's orders now.
* ===========================================================
*/
}
/// <summary>
/// 3. <c>web_visit</c> has no id (declared NoIdColumn): its rows are created together and read with a date range
/// and a link to the account.
/// </summary>
private static async Task Scenario3_ATableWithNoIdAsync(SampleContext dbContext, Dictionary<string, ArxRecordId> accounts)
{
Step("3. A table with no id, read with a date range and a link");
var visits = new[]
{
("ACC-R781", "/pricing", new DateOnly(2026, 3, 10)),
("ACC-R781", "/pricing", new DateOnly(2026, 8, 2)),
("ACC-R781", "/contact", new DateOnly(2026, 9, 15)),
("ACC-R782", "/pricing", new DateOnly(2026, 10, 1)),
}.Select(x =>
{
var visit = new ArxEntity("web_visit");
visit["account_id"] = new ArxEntityReference("account", accounts[x.Item1]);
visit["page"] = x.Item2;
visit["visited_on"] = x.Item3;
return visit;
}).ToList();
await dbContext.Service.CreateMultipleAsync(visits);
var query = new ArxQueryExpression("web_visit");
query.ColumnSet.AddColumns("page", "visited_on");
query.Criteria.AddCondition("visited_on", ArxConditionOperator.GreaterEqual, new DateOnly(2026, 7, 1));
query.Criteria.AddCondition("visited_on", ArxConditionOperator.LessThan, new DateOnly(2026, 10, 1));
var account = query.AddLink("account", "account_id", "id", ArxJoinOperator.Inner);
account.EntityAlias = "acc";
account.ColumnSet.AddColumn("name");
account.LinkCriteria.AddCondition("account_number", ArxConditionOperator.BeginsWith, "ACC-R78");
query.AddOrder("visited_on", ArxOrderType.Ascending);
foreach (var row in (await dbContext.Service.RetrieveMultipleAsync(query)).Entities)
{
Show($"July to September: {row["visited_on"]:yyyy-MM-dd} {row["page"],-9} {row["acc.name"]}");
}
/* ===========================================================
* [DIRECT QUERY CHECK]
* -----------------------------------------------------------
* SELECT v.visited_on, v.page, a.name
* FROM web_visit v
* JOIN account a ON a.id = v.account_id AND a.account_number LIKE 'ACC-R78%'
* WHERE v.visited_on >= '2026-07-01' AND v.visited_on < '2026-10-01'
* ORDER BY v.visited_on;
* -- Expect: 2 rows: 2026-08-02 /pricing, 2026-09-15 /contact (both Summit Supplies).
* ===========================================================
*/
}
}
What every sample is given: the connection string (and the ISample interface the samples implement).
namespace ArxSamples.MySQL;
/// <summary>One documentation sample: a scenario a real application has, shown end to end.</summary>
public interface ISample
{
/// <summary>The name to run it alone: <c>dotnet run -- <name></c>.</summary>
string Name { get; }
/// <summary>One line on what it shows.</summary>
string Title { get; }
Task RunAsync(SampleContext dbContext);
}
/// <summary>
/// What a sample is given. Every sample gets the connection string; the application's service and catalog
/// (SampleContext.Application.cs) and the plain MySqlConnector read-back helper (SampleContext.Direct.cs) live in their own
/// files, so a sample needs only the files it uses.
/// </summary>
public sealed partial class SampleContext
{
public SampleContext(string connectionString)
{
ConnectionString = connectionString;
}
public string ConnectionString { get; }
}
How the samples print: Step for each scenario, Show for what it did, ShowError for an error caught on purpose.
using ARX.SDK;
namespace ArxSamples.MySQL;
/// <summary>How the samples print: a numbered step for each scenario, then what it did.</summary>
public static class SampleOutput
{
/// <summary>The start of a scenario: <c>Step("1. By the id Create returned")</c>.</summary>
public static void Step(string text) => Console.WriteLine($" > {text}");
/// <summary>What the scenario did.</summary>
public static void Show(string text) => Console.WriteLine($" {text}");
/// <summary>An ARX error the scenario caught on purpose.</summary>
public static void ShowError(ArxException exception)
=> Console.WriteLine($" caught {exception.GetType().Name}: {exception.Message}");
}
The application's ARX service and its schema catalog, created once and shared by the samples.
using ARX.SDK.MySQL.Services;
using ARX.SDK.Services;
namespace ArxSamples.MySQL;
/// <summary>The application's ARX service and its schema catalog, shared by the real and advanced samples.</summary>
public sealed partial class SampleContext
{
private ArxSchemaCatalog? _catalog;
private ArxMySqlDbService? _service;
/// <summary>The application's schema catalog: table ids, keys and selection sets (SampleCatalog.cs).</summary>
public ArxSchemaCatalog Catalog => _catalog ??= SampleCatalog.Build();
/// <summary>
/// One service for the whole application. It holds no connection: every call opens one from the MySqlConnector pool and
/// closes it, unless you pass your own connection or transaction.
/// </summary>
public ArxMySqlDbService Service => _service ??= new ArxMySqlDbService(ConnectionString, Catalog);
}
The application's schema catalog: every table's id column and keys, and its selection sets.
using ARX.SDK.Services;
using System.Text.Json;
using System.Text.Json.Serialization;
namespace ArxSamples.MySQL;
/// <summary>An account's industry. Stored in account.industry (SMALLINT) as the enum's number.</summary>
public enum Industry : short
{
Retail = 1,
Manufacturing = 2,
Healthcare = 3,
Finance = 4,
Technology = 5
}
/// <summary>
/// The application's schema catalog: every table's id column and keys, and every picklist (selection set),
/// defined once.
/// </summary>
/// <remarks>
/// <para>
/// <b>Ids.</b> Every table the application writes is declared with its one id column: its name, its .NET type, and
/// whether the database generates it (<c>ArxIdColumn.Generated</c>: identity, sequence, default) or the caller supplies
/// it (<c>ArxIdColumn.Supplied</c>: a natural id, a client-generated Guid). A table with no id column, such as a log or a
/// table identified by several columns together, is declared <c>ArxIdColumn.NoIdColumn</c>. ARX never reads ids from
/// the database: the developer knows the schema, and an undeclared table is refused (ARX1016).
/// </para>
/// <para>
/// <b>Keys.</b> Optional business keys: one or more columns whose values identify a record, such as an account number,
/// or a region and a SKU together. Create doesn't use them (the database's unique constraints do the enforcing); Update
/// and Delete will be able to find rows by them. <c>ValidateSchemaAsync</c> checks ids and keys against the database
/// when you ask it to.
/// </para>
/// <para>
/// <b>Selection sets.</b> /// A selection set (picklist, option set) is a column that only accepts a fixed list of codes, each with a display
/// text: an account's status (ACTIVE, ON_HOLD, CLOSED), a contact's preferred channel (E, P, S). The catalog tells ARX,
/// for each set:
/// </para>
/// <list type="bullet">
/// <item><b>Name</b>: what an <see cref="ArxSelectionSetValue"/> refers to, for example <c>new ArxSelectionSetValue("AccountStatus", "ON_HOLD")</c>.</item>
/// <item><b>Kind</b>: what the codes are, matching the column: Integer, String, Character, Boolean, Decimal or Guid.
/// (A fixed list of text values is a String set, whether the column is an ENUM or a VARCHAR that a CHECK guards.)</item>
/// <item><b>Multiplicity</b>: Single (one code), or several codes stored as bit flags (Flags), a delimited string
/// (Delimited) or a JSON array (Json). MySQL has no array columns.</item>
/// <item><b>Options</b>: each code with its display text and order. A retired option (<c>IsActive: false</c>) stays
/// readable in old rows, but can't be written any more.</item>
/// </list>
/// <para>
/// Build the catalog once at startup and give it to the service: <c>new ArxMySqlDbService(connectionString, SampleCatalog.Build())</c>.
/// ARX checks every <see cref="ArxSelectionSetValue"/> against it in memory, before any SQL is sent, and stores the code
/// itself in the column: no lookup table, no extra query. A plain value (a string or number that isn't an
/// ArxSelectionSetValue) isn't checked.
/// </para>
/// <para>
/// The catalog is plain code, so the options can come from wherever you keep them: written out here, taken from a .NET
/// enum (<c>AddEnum</c>), loaded from JSON (<see cref="SetsJson"/> and <see cref="FromJson"/> below), or loaded at
/// startup from your own option table and passed to <c>new ArxSelectionSetDefinition(name, kind, options)</c>. ARX
/// never reads option tables or files itself.
/// </para>
/// </remarks>
public static class SampleCatalog
{
/// <summary>
/// Selection sets kept as JSON, as an application might keep them in a file, a settings store or a database column.
/// Here the JSON is in the class itself; in an application, read it from wherever you keep it
/// (<c>File.ReadAllText("selection-sets.json")</c>, configuration, an HTTP call) and pass it to <see cref="FromJson"/>.
/// "multiplicity" and "active" are optional (Single and true).
/// </summary>
public const string SetsJson = """
[
{
"name": "LeadSource",
"kind": "String",
"options": [
{ "value": "WEB", "text": "Website", "order": 0 },
{ "value": "REFERRAL", "text": "Referral", "order": 1 },
{ "value": "EVENT", "text": "Trade show", "order": 2 },
{ "value": "COLD_CALL", "text": "Cold call", "order": 3, "active": false }
]
},
{
"name": "ContactRating",
"kind": "Integer",
"multiplicity": "Single",
"options": [
{ "value": 1, "text": "Poor" },
{ "value": 2, "text": "Fair" },
{ "value": 3, "text": "Good" },
{ "value": 4, "text": "Very good" },
{ "value": 5, "text": "Excellent" }
]
}
]
""";
public static ArxSchemaCatalog Build()
{
var builder = ArxSchemaCatalog.Create()
// ---------- tables: id column and keys ----------
// Generated BIGINT ids (AUTO_INCREMENT): the database fills them in. The keys are the unique columns that also
// identify a record.
.Table("account", ArxIdColumn.Generated<long>("id")).Key("account", "account_number")
.Table("contact", ArxIdColumn.Generated<long>("id")).Key("contact", "email")
// Retrieve: a contact's account_id reads back as a reference to its account, named by the account's
// name; a contact is named by its first and last names.
.Lookup("contact", "account_id", "account")
.DisplayName("account", "name")
.DisplayName("contact", new[] { "first_name", "last_name" }, " ")
.Table("product_category", ArxIdColumn.Generated<long>("id")).Key("product_category", "name")
.Table("product", ArxIdColumn.Generated<long>("id")).Key("product", "sku")
.Table("sales_order", ArxIdColumn.Generated<long>("id")).Key("sales_order", "order_number")
.Table("order_line", ArxIdColumn.Generated<long>("id"))
.Table("data_type_showcase", ArxIdColumn.Generated<long>("id"))
// A natural id: the caller gives the ISO country code.
.Table("country", ArxIdColumn.Supplied<string>("code"))
// A Guid id the application gives (CHAR(36)): MySQL can only hand back generated integer ids.
.Table("device", ArxIdColumn.Supplied<Guid>("id")).Key("device", "serial_number")
// No id column: a price is identified by its region and SKU together, a compound key.
.Table("price_list", ArxIdColumn.NoIdColumn).Key("price_list", "region", "sku")
// No primary key at all: the same action can be logged twice.
.Table("activity_log", ArxIdColumn.NoIdColumn)
// A table without an id: a visit is a fact, never updated (Retrieve Advanced8).
.Table("web_visit", ArxIdColumn.NoIdColumn)
// ---------- selection sets ----------
// From a .NET enum: the set is named after the enum ("Industry"), the codes are its numbers (Retail = 1, …),
// the display texts are its member names. Column: account.industry SMALLINT.
.AddEnum<Industry>()
// Written out: String codes with display texts, single choice. Column: account.status VARCHAR(10).
.Add("AccountStatus", ArxSelectionSetKind.String, ("ACTIVE", "Active"), ("ON_HOLD", "On hold"), ("CLOSED", "Closed"))
// Multiple choice, stored as delimited text ("ENTERPRISE,PUBLIC"). RESELLER is retired: rows that have it still
// read back, but new writes can't use it. Column: account.segments VARCHAR(200).
.Add(new ArxSelectionSetDefinition("CustomerSegment", ArxSelectionSetKind.String, new[]
{
new ArxSelectionSetOption("SMB", "Small business", 0),
new ArxSelectionSetOption("ENTERPRISE", "Enterprise", 1),
new ArxSelectionSetOption("PUBLIC", "Public sector", 2),
new ArxSelectionSetOption("RESELLER", "Reseller", 3, IsActive: false)
}, ArxSelectionSetMultiplicity.Delimited))
// Single-character codes. Column: contact.preferred_channel CHAR(1).
.Add("ContactChannel", ArxSelectionSetKind.Character, ('E', "Email"), ('P', "Phone"), ('S', "Text message"))
// A fixed list of text values, in a MySQL ENUM column, which allows only its labels.
// Column: data_type_showcase.mood ENUM('happy', 'neutral', 'sad').
.Add(new ArxSelectionSetDefinition("Mood", ArxSelectionSetKind.String, new[]
{
new ArxSelectionSetOption("happy", "Happy", 0),
new ArxSelectionSetOption("neutral", "Neutral", 1),
new ArxSelectionSetOption("sad", "Sad", 2)
}));
// Loaded from JSON: LeadSource (contact.lead_source VARCHAR(50)) and ContactRating (contact.rating SMALLINT).
foreach (var set in FromJson(SetsJson))
{
builder.Add(set);
}
return builder.Build();
}
/// <summary>Reads selection set definitions from JSON (the shape of <see cref="SetsJson"/>).</summary>
public static IEnumerable<ArxSelectionSetDefinition> FromJson(string json)
{
var options = new JsonSerializerOptions
{
PropertyNameCaseInsensitive = true,
Converters = { new JsonStringEnumConverter() } // "String", "Integer", "Array", … as names
};
var sets = JsonSerializer.Deserialize<List<JsonSet>>(json, options)
?? throw new InvalidOperationException("The selection set JSON is empty.");
foreach (var set in sets)
{
yield return new ArxSelectionSetDefinition(
set.Name,
set.Kind,
set.Options.Select(x => new ArxSelectionSetOption(Code(x.Value, set.Kind), x.Text, x.Order, x.Active)),
set.Multiplicity,
set.DatabaseTypeName);
}
}
/// <summary>A JSON value as a code of the set's kind: JSON has no char, Guid or 64-bit integer of its own.</summary>
private static object Code(JsonElement value, ArxSelectionSetKind kind) => kind switch
{
ArxSelectionSetKind.Integer => value.GetInt64(),
ArxSelectionSetKind.Decimal => value.GetDecimal(),
ArxSelectionSetKind.Boolean => value.GetBoolean(),
ArxSelectionSetKind.Guid => value.GetGuid(),
ArxSelectionSetKind.Character => value.GetString()![0],
_ => value.GetString()! // String and DatabaseEnum
};
private sealed record JsonSet(
string Name,
ArxSelectionSetKind Kind,
List<JsonOption> Options,
ArxSelectionSetMultiplicity Multiplicity = ArxSelectionSetMultiplicity.Single,
string? DatabaseTypeName = null);
private sealed record JsonOption(JsonElement Value, string Text, int Order = 0, bool Active = true);
}
Expected output
What dotnet run printed when the sample was verified, on a freshly created sample schema. Ids differ when the tables already hold rows.
> 1. A view in another schema, linked to a table and aggregated
SKU-R781 Hammer 5 sold (entity name: arx_samples_reporting.vw_product_catalogue)
SKU-R782 Saw 2 sold (entity name: arx_samples_reporting.vw_product_catalogue)
> 2. A summary view: always up to date
Summit Supplies orders 2, revenue 380.00
Harbor Hardware orders 1, revenue 115.00
a new order for Harbor: the view says 2 orders, 615.00; the tables say 2 orders, 615.00
> 3. A table with no id, read with a date range and a link
July to September: 2026-08-02 /pricing Summit Supplies
July to September: 2026-09-15 /contact Summit Supplies