C#
ServiceCollection
Learn Microsoft.Extensions.DependencyInjection ServiceCollection.
ServiceCollection
Microsoft.Extensions.DependencyInjection.ServiceCollection is .NET's official DI container. You register services with AddTransient, AddScoped or AddSingleton; you produce a provider with BuildServiceProvider().
From the provider you retrieve a registered service with provider.GetRequiredService<T>(). The container resolves dependencies automatically: if a service requires another dependency, the container instantiates and passes it too. This is a major convenience in mid-sized and large applications.
IServiceCollection
IServiceCollection is the interface; ServiceCollection is its implementation. Many .NET libraries take IServiceCollection for registration, so you depend on the interface rather than the concrete class.
Registration usually maps an interface to an implementation: services.AddTransient<ILogger, ConsoleLogger>(). This makes requests for ILogger return a ConsoleLogger instance. To change the implementation you only change the registration; consumers stay the same.
Exercise Register and resolve a service
In Main, create the container with var services = new ServiceCollection();. Register with services.AddTransient<ILogger, ConsoleLogger>();. Build the provider with var provider = services.BuildServiceProvider();. Get the logger with var logger = provider.GetRequiredService<ILogger>(); and print with logger.Log("Hello");.
Show example solution
var services = new ServiceCollection(); services.AddTransient<ILogger, ConsoleLogger>(); var provider = services.BuildServiceProvider(); var logger = provider.GetRequiredService<ILogger>(); logger.Log("Hello");
Example solution:
using System;
using Microsoft.Extensions.DependencyInjection;
interface ILogger { void Log(string msg); }
class ConsoleLogger : ILogger
{
public void Log(string msg) => Console.WriteLine(msg);
}
class Program
{
static void Main()
{
var services = new ServiceCollection();
services.AddTransient<ILogger, ConsoleLogger>();
var provider = services.BuildServiceProvider();
var logger = provider.GetRequiredService<ILogger>();
logger.Log("Hello");
}
}
Test yourself
-
Match the method to its behavior
- AddTransient
- New each time
- AddScoped
- Per scope
- AddSingleton
- Single instance
- BuildServiceProvider
- Builds provider
-
Complete the AddTransient registration
services.____<ILogger, ConsoleLogger>();
Show answer
services.AddTransient<ILogger, ConsoleLogger>();
-
How are services registered in ServiceCollection?
- With AddTransient/AddScoped/AddSingleton
- By calling Add directly
- Only with the new keyword
- With the Configure method
Show answer
With AddTransient/AddScoped/AddSingleton — Correct. Services are registered with AddTransient/AddScoped/AddSingleton.
Next lesson: Lifetime: Singleton
