DKNet

Describe database sequences with enum metadata

Part of DKNet.EfCore.Abstractions. Put [SqlSequence] on an enum and [Sequence] on each member that represents a database sequence.

Use the console-project setup in the Quick Start, then replace Program.cs with this example.

using DKNet.EfCore.Abstractions.Attributes;

var field = typeof(InvoiceSequences).GetField(nameof(InvoiceSequences.Number))!;
var rule = (SequenceAttribute)Attribute.GetCustomAttribute(field, typeof(SequenceAttribute))!;
Console.WriteLine(rule.StartAt); // 1000

[SqlSequence("billing")]
public enum InvoiceSequences
{
    [Sequence(typeof(long), StartAt = 1000, FormatString = "INV-{1:000000}")]
    Number
}

SqlSequence supplies a schema and Sequence supplies per-enum-member settings consumed during relational model configuration.

The metadata declares no database objects itself. Extensions registers Seq_<Member> on SQL Server or Npgsql models and reads the next value.

⚙️ Configuration reference

Option	Type	Default	Effect
`SqlSequence.Schema`	`string`	`"seq"`	Schema for the enum.
`Sequence.Type`	`Type`	`typeof(int)`	Numeric sequence type.
`StartAt`, `Min`, `Max`	`long`	`-1`	Apply positive values; otherwise keep database defaults.
`IncrementsBy`	`int`	`-1`	Apply a positive step.
`Cyclic`	`bool`	`true`	Configure wraparound.
`FormatString`	`string?`	`null`	`{1}` is the number; `DateTime` is rewritten to argument `{0}` using UTC and invariant formatting.

🧱 Where it fits

The domain carries enum metadata. Extensions reads that metadata during supported-provider model building and uses it again when the host asks for a sequence value.

The package component map shows the host, contracts and consumers involved in this capability.

⚠️ Gotchas & limits

[Sequence] targets fields, not entity properties. Enum members lacking it are skipped during model registration.
Only byte, short, int and long are accepted; another type throws NotSupportedException when the attribute is constructed.
Numeric settings are applied only when greater than zero. Zero and negative increments cannot be expressed through this registration.

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