ASP.NET
Core Dependency
Injection
▌Introduction
This article
shows how to use injected services that implement the same interface.
Notice that from DOTNET 8, it supports the Keyed Services to retrieve the specified implement instance of the same interface. See Anderew Lock's article: Keyed service dependency injection container support.
▌Environment
▋ASP.NET Core 3.1.102
▌Implement
Assume that we
implement an interface: IKeyService, by 3 classes:
·
TripleDesKeyService
·
SharedSecretService
·
RsaKeyService
And inject them
like following,
public void ConfigureServices(IServiceCollection services)
{
services.AddSingleton<IKeyService, TripleDesKeyService>();
services.AddSingleton<IKeyService, SharedSecretKeyService>();
services.AddSingleton<IKeyService, RsaKeyService>();
}
Here are some ways
to request the injected instances in other services.
▋Request as IEnumerable collection and resolve
private readonly TripleDesKeyService tripleDesKeyService = null;
private readonly SharedSecretKeyService sharedSecretKeyService = null;
private readonly RsaKeyService rsaKeyService= null;
public MyService(IEnumerable<IKeyService> keyServices)
{
// Revolve
instance
this.tripleDesKeyService = keyServices.FirstOrDefault(x => x.GetType().Equals(typeof(TripleDesKeyService))) as TripleDesKeyService;
this.sharedSecretKeyService = keyServices.FirstOrDefault(x => x.GetType().Equals(typeof(SharedSecretKeyService))) as SharedSecretKeyService;
this.rsaKeyService = keyServices.FirstOrDefault(x => x.GetType().Equals(typeof(RsaKeyService))) as RsaKeyService;
}
▋Create a resolver delegate
public delegate IKeyService KeyServiceResolver(string className);
/// <summary>
/// ServiceCollectionExtensions
/// </summary>
public static class ServiceCollectionExtensions
{
public static IServiceCollection AddCustomServices(this IServiceCollection services)
{
services.AddSingleton<IKeyService, TripleDesKeyService>();
services.AddSingleton<IKeyService, SharedSecretKeyService>();
services.AddSingleton<IKeyService, RsaKeyService>();
services.AddSingleton<KeyServiceResolver>(sp => className =>
{
var keyService = sp.GetServices<IKeyService>().Where(x => x.GetType().Name.Equals(className)).FirstOrDefault();
return keyService;
});
return services;
}
}
And then request
the Resolver to resolve the instances:
private readonly TripleDesKeyService tripleDesKeyService = null;
private readonly SharedSecretKeyService sharedSecretKeyService = null;
private readonly RsaKeyService rsaKeyService= null;
public MyService(KeyServiceResolver keyServiceResolver)
{
this.tripleDesKeyService = keyServiceResolver(nameof(TripleDesKeyService)) as TripleDesKeyService;
this.sharedSecretKeyService = keyServiceResolver(nameof(SharedSecretService)) as SharedSecretService;
this.rsaKeyService = keyServiceResolver(nameof(RsaKeyService)) as RsaKeyService;
}
▌Reference
▋N/A
