Strategy

Namespace: DesignPatterns.Behavioral

Overview

Register algorithm implementations by key at compile time. Avoid large switch blocks while keeping selection logic in your application code.

Runtime

• IStrategyRegistry<TKey, TStrategy> — Get / TryGet
• StrategyRegistryBuilder<TKey, TStrategy> — manual registration

Source generator

1. Declare a partial static registry holder.
2. Mark each implementation with [RegisterStrategy(typeof(TContract), "key")].
3. Generator emits {Name}Keys, Instance (eager registry), and optional RegisterDi.

[RegisterStrategy(typeof(IPaymentStrategy), "alipay")]
public sealed class AlipayPayment : IPaymentStrategy { ... }

public static partial class PaymentStrategyRegistry { }

Optional marker interfaces: IStrategy<TIn, TOut>, IAsyncStrategy<TIn, TOut> — not required by the generator.

Async resolution

IAsyncStrategy contracts use the same Keys / Registry / RegisterDi pipeline. StrategyRegistryExtensions adds ExecuteAsync and TryExecuteAsync:

public interface ITextProcessor : IAsyncStrategy<string, int> { }

// Registry value is IAsyncStrategy<TIn, TOut>
await registry.ExecuteAsync(key, input);

// Derived contract (specify TContract, TOutput, TInput)
await registry.ExecuteAsync<ITextProcessor, int, string>(TextProcessorKeys.Length, "hello");

// Equivalent
await registry.Get(TextProcessorKeys.Length).ExecuteAsync("hello");

Diagnostics

DP003–DP007 — duplicate keys, contract mismatch, unregistered types (DP006 + CodeFix), missing ctor. DP025 for unknown literal keys at lookup sites. See Registry key conventions.

Sample

DesignPatterns.Samples.Strategy — sync payment strategies plus async IRefundProcessor with ExecuteAsync (RefundProcessors.cs).

DI

See Dependency Injection for RegisterDi.

Maintainer doc: docs/Strategy.md (中文).