PoliNorError.Extensions.DependencyInjection

The PoliNorError.Extensions.DependencyInjection package extends PoliNorError library to provide integration with Microsoft Dependency Injection.

⚡ Quick Start

Get up and running in 3 simple steps:

1. Register policies in DI

// Program.cs / Startup.cs
services.AddPoliNorError(
	Assembly.GetExecutingAssembly());

This scans your assembly for all IPolicyBuilder<> implementations and wires up IPolicy<T> automatically.

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2. Define your policy builders

public class SomePolicyBuilder : IPolicyBuilder<SomePolicyBuilder>
{
    private readonly ILoggerFactory _logger;
    public SomePolicyBuilder(ILoggerFactory logger) => _logger = logger;

    public IPolicyBase Build() =>
        new RetryPolicy(3)
            .WithErrorProcessor(new RetryLoggingErrorProcessor<SomePolicyBuilder>(
                _logger.CreateLogger<SomePolicyBuilder>()))
            .WithWait(TimeSpan.FromSeconds(3));
}

Another example:

public class AnotherPolicyBuilder : IPolicyBuilder<AnotherPolicyBuilder>
{
    private readonly ILoggerFactory _logger;
    public AnotherPolicyBuilder(ILoggerFactory logger) => _logger = logger;

    public IPolicyBase Build() =>
        new RetryPolicy(2)
            .WithErrorProcessor(new RetryLoggingErrorProcessor<AnotherPolicyBuilder>(
                _logger.CreateLogger<AnotherPolicyBuilder>()))
            .WithWait(TimeSpan.FromSeconds(1));
}

, where RetryLoggingErrorProcessor<T>:

class RetryLoggingErrorProcessor<T> : ErrorProcessor
{
    private readonly ILogger<T> _logger;

    public RetryLoggingErrorProcessor(ILogger<T> logger) => _logger = logger;

    public override void Execute(Exception error,
        ProcessingErrorInfo? info = null,
        CancellationToken token = default)
    {
        _logger.LogError(error,
            "An error occurred while doing work on {Attempt} attempt.",
            info.GetRetryCount() + 1);
    }
}

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3. Consume policies in your services

public class Worker
{
    private readonly IPolicy<SomePolicyBuilder> _somePolicy;
    private readonly IPolicy<AnotherPolicyBuilder> _anotherPolicy;

    public Worker(IPolicy<SomePolicyBuilder> somePolicy,
                  IPolicy<AnotherPolicyBuilder> anotherPolicy)
    {
        _somePolicy = somePolicy;
        _anotherPolicy = anotherPolicy;
    }

    public async Task DoWorkAsync(CancellationToken token)
    {
        var result1 = await _somePolicy.HandleAsync(MightThrowAsync, false, token).ConfigureAwait(false);
        var result2 = await _anotherPolicy.HandleAsync(MightThrowAsync, false, token).ConfigureAwait(false);
    }

    private async Task MightThrowAsync(CancellationToken token)
    {
        await Task.Delay(100, token);
        throw new SomeException("Something went wrong.");
    }
}

✅ That’s it!

• Builders encapsulate configuration.
• Consumers inject IPolicy<T> and just use it.
• DI takes care of wiring everything together.

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✨ Key Features

• IPolicyBuilder

  • Implemented only in your builders.
  • A builder abstraction for creating policies.
  • Encapsulates configuration (retry count, wait strategy, error processors, etc.).
  • Registered automatically into DI via assembly scanning.

• IPolicy

  • Consumed only in your services.
  • A closed generic wrapper that represents a policy built by a specific builder.
  • Resolved directly from DI, giving consumers a type-safe handle to the correct policy.
  • Internally backed by ProxyPolicy<T> which delegates to the builder’s Build() result.

• Automatic DI Registration

  • AddPoliNorError() scans assemblies for all IPolicyBuilder<> implementations.
  • Registers them and wires up IPolicy<T> → ProxyPolicy<T> automatically.

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🧩 How It Works

1. You create builder classes that implement IPolicyBuilder<TBuilder>.
2. AddPoliNorError registers the open generic mapping IPolicy<> -> ProxyPolicy<>.
3. When a consumer requests IPolicy<TBuilder>, DI resolves ProxyPolicy<TBuilder>.
4. The proxy calls the builder’s Build() method to produce the actual policy.
5. All calls (Handle, HandleAsync, etc.) are delegated to the built policy.

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✅ Benefits

• Type-safe DI: No string keys or manual lookups.
• Separation of concerns: Builders configure, consumers execute.
• Discoverable: Constructor injection makes dependencies explicit.
• Testable: Swap out builders or inject fake policies in tests.
• Extensible: Add new PoliNorError policies by just adding new builders.

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🏆 Samples

See samples folder for concrete example.

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