MetaInject

MetaInject is a simple and powerful Dependency Injection (DI) tool for .NET. With the [MetaInject] attribute, you can inject dependencies directly into properties or fields without needing a constructor. MetaInject works seamlessly with ASP.NET Core and other .NET projects, simplifying dependency management.

Features

• [MetaInject] attribute: Enables property injection, allowing dependencies to be injected into properties instead of using constructors.
• Seamless Web API Integration: Fully compatible with ASP.NET Core and other .NET-based projects.

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Getting Started

Prerequisites

• .NET 8 or higher.

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Usage

Use the following namespaces:

using MetaInject.Core.Attributes; using MetaInject.Extensions;

Scenario: Injecting dependencies without a constructor

When you have a service with a large number of parameters, such as a service constructor with over 7 parameters, using a constructor can become cumbersome. MetaInject simplifies this by allowing you to inject dependencies directly into properties.

Before MetaInject (constructor injection)

public class ComplexService : IComplexService { private readonly IUserService _userService; private readonly IAddressService _addressService; private readonly INotesService _notesService; private readonly IContractService _contractService; public ComplexService( IUserService userService, IAddressService addressService, INotesService notesService, IContractService contractService) { _userService = userService; _addressService = addressService; _notesService = notesService; _contractService = contractService; } }

After MetaInject (property injection)

With MetaInject, you can remove the constructor and inject dependencies directly into properties. The property must:

• be virtual
• have both a getter and a setter

public class ComplexService : IComplexService { [MetaInject] public virtual required IUserService UserService { get; init; } [MetaInject] public virtual required IAddressService AddressService { get; init; } [MetaInject] public virtual required INotesService NotesService { get; init; } [MetaInject] public virtual required IContractService ContractService { get; init; } }

or

public class ComplexService : IComplexService { [MetaInject] public virtual IUserService UserService { get; set; } [MetaInject] public virtual IAddressService AddressService { get; set; } [MetaInject] public virtual INotesService NotesService { get; set; } [MetaInject] public virtual IContractService ContractService { get; set; } }

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Use in Minimal API .NET 8

Use .AddMetaInject() for advanced DI functionality:

// Registering sample services with the DI container builder.Services.AddSingleton<IGreetingService, GreetingService>(); builder.Services.AddScoped<IUserService, UserService>(); builder.Services.AddScoped<IAddressService, AddressService>(); builder.Services.AddScoped<IContractService, ContractService>(); builder.Services.AddScoped<INotesService, NotesService>(); builder.Services.AddScoped<IComplexService, ComplexDefaultService>(); builder.Services.AddScoped<IComplexFieldsService, ComplexFieldsService>(); builder.Services.AddScoped<IComplexPropertiesService, ComplexPropertiesService>(); // Register MetaInject for advanced DI functionality (should be last in the order) builder.Services.AddMetaInject();

Use the service in API:

app.MapGet("api/app2/GetCurrentInfo", (IComplexPropertiesService service) => { return Results.Ok(service.GetCurrentInfo()); }) .WithMetadata() .WithTags("Properties implementation") .WithDescription( "Retrieves information using the [ComplexPropertiesService] implementation. The service uses 'virtual' properties injected with the [MetaInject] attribute.") .WithOpenApi();

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Use in console application .NET 8

Use .AddMetaInject() for advanced DI functionality:

using var host = Host.CreateDefaultBuilder(args) .ConfigureServices(services => { // Registering sample services with the DI container services.AddSingleton<ILoggerService, LoggerService>(); services.AddScoped<IAddressService, AddressService>(); services.AddTransient<IUserService, UserService>(); services.AddTransient<IClientService, ClientService>(); // Register MetaInject for advanced DI functionality (should be last in the order) services.AddMetaInject(); }) .Build();

Use the service in console application:

var userService = host.Services .GetRequiredService<IUserService>();