Bobbysoft.Extensions.DependencyInjection.ServiceDecoration

ServiceDecorator

This light weight class library is used to decorate already dependency injected classes inside the Microsoft.Extensions.DependencyInjection.IServiceCollection.

---

The quick overview

using Bobbysoft.Extensions.DependencyInjection; public void DecorateServices(IServiceCollection services) { // ***ServiceDecorator.Decorate is the extension method added with this Library services.Decorate<ILogger>( subject => new LoggerDecorator(subject)); } using Bobbysoft.Extensions.DependencyInjection; public void DecorateServices(IServiceCollection services) { // ***ServiceDecorator.Decorate is the extension method added with this Library services.Decorate<ILogger>( (subject, provider) => new LoggerDecorator(subject, provider.GetRequiredService<Emailer>())); }

---

Step 1: make sure you know what a decorator is

• GOF Decorator Design pattern
• Excellent explanation by Shiv Kumar youtube

Step 2: decide which class to decorate

I choose the SeriLogger from SeriLog that is registered with the ILogger interface. It does not matter if the interface is an abstract class interface or an c#-Interface-Interface I could have picked any of the two for this tutorial.

Step 3: write a decorator to the chosen abstraction

internal class LoggerDecorator : ILogger { private readonly ILogger _logger; public LoggerDecorator(ILogger logger) { _logger = logger; } public void Write(LogEvent logEvent) { DecorateLogEvent(logEvent); _logger.Write(logEvent); } private void DecorateLogEvent(LogEvent logEvent) { // Decorate your logEvent here } }

Step 4: Register both Service (abstraction) and implementation in the IServiceCollection

public void ConfigureServices(IServiceCollection services) { services.AddLogging(loggingBuilder => loggingBuilder.AddSerilog(dispose: true)); // Other services ... }

Step 5: Decorate the ServiceCollection from the outside of the IServiceCollection

using Bobbysoft.Extensions.DependencyInjection; public void DecorateServices(IServiceCollection services) { // ***ServiceDecorator.Decorate is the extension method added with this Library services.Decorate<ILogger>( subject => new LoggerDecorator(subject)); }

---

The other way - with multiple dependencies

Add a modified decorator

internal class LoggerDecorator : ILogger { private readonly ILogger _logger; private readonly Emailer _emailer; // We are adding a second dependency Emailer public LoggerDecorator(ILogger logger, Emailer emailer) { _logger = logger; _emailer = emailer; } public void Write(LogEvent logEvent) { DecorateLogEvent(logEvent); _emailer.Send(logEvent); _logger.Write(logEvent); } private void DecorateLogEvent(LogEvent logEvent) { // Decorate your logEvent here } }

Register both implementations services

using Bobbysoft.Extensions.DependencyInjection; public void ConfigureServices(IServiceCollection services) { services.AddLogging(loggingBuilder => loggingBuilder.AddSerilog(dispose: true)); services.AddTransient<Emailer>(); // Other services ... } public void DecorateServices(IServiceCollection services) { // ***ServiceDecorator.Decorate is the extension method added with this Library services.Decorate<ILogger>( (subject, provider) => new LoggerDecorator(subject, provider.GetService<Emailer>())); }

If in doubt look at the different examples in the test project