c# - How to inject constructor which has two times the same interface with Autofac

C# - How to inject constructor which has two times the same interface with Autofac

When using Autofac for dependency injection in a C# project, you may encounter a scenario where you need to inject multiple implementations of the same interface into a constructor. Autofac provides a way to handle this situation by using named registrations or key-based resolution.

Here's how you can achieve this:

Step 1: Define Your Interfaces and Implementations

First, define your interface and its implementations. For example:

public interface IService { void Execute(); } public class FirstService : IService { public void Execute() { Console.WriteLine("FirstService Executing"); } } public class SecondService : IService { public void Execute() { Console.WriteLine("SecondService Executing"); } }

Step 2: Register Your Services with Autofac

Next, register these services with Autofac, assigning them different names or keys to distinguish between the implementations.

var builder = new ContainerBuilder(); builder.RegisterType<FirstService>().Named<IService>("firstService"); builder.RegisterType<SecondService>().Named<IService>("secondService"); // Register the consumer class builder.RegisterType<MyClass>(); var container = builder.Build();

Step 3: Inject Named Services into the Constructor

Modify the constructor of the class that requires these services to accept parameters with named services.

public class MyClass { private readonly IService _firstService; private readonly IService _secondService; public MyClass([Named("firstService")] IService firstService, [Named("secondService")] IService secondService) { _firstService = firstService; _secondService = secondService; } public void DoWork() { _firstService.Execute(); _secondService.Execute(); } }

Step 4: Resolve and Use Your Class

Finally, resolve MyClass from the container and use it.

var myClass = container.Resolve<MyClass>(); myClass.DoWork();

Complete Example

Here's the complete example in one place:

using Autofac; using System; public interface IService { void Execute(); } public class FirstService : IService { public void Execute() { Console.WriteLine("FirstService Executing"); } } public class SecondService : IService { public void Execute() { Console.WriteLine("SecondService Executing"); } } public class MyClass { private readonly IService _firstService; private readonly IService _secondService; public MyClass([Named("firstService")] IService firstService, [Named("secondService")] IService secondService) { _firstService = firstService; _secondService = secondService; } public void DoWork() { _firstService.Execute(); _secondService.Execute(); } } public class Program { public static void Main(string[] args) { var builder = new ContainerBuilder(); builder.RegisterType<FirstService>().Named<IService>("firstService"); builder.RegisterType<SecondService>().Named<IService>("secondService"); builder.RegisterType<MyClass>(); var container = builder.Build(); var myClass = container.Resolve<MyClass>(); myClass.DoWork(); } }

Explanation

  • Named Registrations: Use .Named<IService>("firstService") and .Named<IService>("secondService") to differentiate between the two implementations of IService.
  • Named Attribute: Use [Named("firstService")] and [Named("secondService")] in the constructor of MyClass to specify which implementation should be injected.

This approach allows you to inject multiple implementations of the same interface into a class using Autofac.

Examples

  1. "Autofac constructor injection with two instances of same interface C#"

    Description: This query addresses users trying to inject a constructor with two parameters of the same interface using Autofac in C#.

    builder.RegisterType<ImplementationA>().As<IService>(); builder.RegisterType<ImplementationB>().As<IService>(); builder.RegisterType<MyClass>().As<IMyClass>();

    This code snippet registers two different implementations (ImplementationA and ImplementationB) for the IService interface, and then registers MyClass which has a constructor that takes two IService parameters.

  2. "Autofac resolve constructor with duplicate interface C#"

    Description: Users encountering issues resolving a constructor with duplicate interface parameters using Autofac in C# can refer to this query.

    public class MyClass : IMyClass { public MyClass(IService serviceA, IService serviceB) { // Constructor logic } }

    This code snippet defines a class MyClass with a constructor that takes two parameters of the same interface IService.

  3. "C# Autofac multiple constructor parameters same interface"

    Description: This query is for users looking for a solution to inject multiple parameters of the same interface into a constructor using Autofac in C#.

    builder.RegisterType<ImplementationA>().As<IService>(); builder.RegisterType<ImplementationB>().As<IService>(); 
    public class MyClass : IMyClass { public MyClass(IService serviceA, IService serviceB) { // Constructor logic } }

    This code snippet registers two different implementations (ImplementationA and ImplementationB) for the IService interface, and then defines a class MyClass with a constructor that takes two IService parameters.

  4. "Autofac resolve constructor with same interface twice C#"

    Description: Users trying to resolve a constructor with the same interface injected twice using Autofac in C# can refer to this query.

    public class MyClass : IMyClass { public MyClass(IService serviceA, IService serviceB) { // Constructor logic } }

    This code snippet defines a class MyClass with a constructor that takes two parameters of the same interface IService.

  5. "Inject two instances of same interface with Autofac C#"

    Description: This query addresses users attempting to inject two instances of the same interface into a constructor using Autofac in C#.

    builder.RegisterType<ImplementationA>().As<IService>(); builder.RegisterType<ImplementationB>().As<IService>();

    This code snippet registers two different implementations (ImplementationA and ImplementationB) for the IService interface.

  6. "Autofac register multiple implementations of same interface C#"

    Description: Users looking to register multiple implementations of the same interface using Autofac in C# can refer to this query.

    builder.RegisterType<ImplementationA>().As<IService>(); builder.RegisterType<ImplementationB>().As<IService>();

    This code snippet registers two different implementations (ImplementationA and ImplementationB) for the IService interface.

  7. "Autofac constructor injection with duplicate interface C#"

    Description: This query is for users trying to perform constructor injection with duplicate interface parameters using Autofac in C#.

    public class MyClass : IMyClass { public MyClass(IService serviceA, IService serviceB) { // Constructor logic } }

    This code snippet defines a class MyClass with a constructor that takes two parameters of the same interface IService.

  8. "Autofac resolve constructor with two times same interface C#"

    Description: Users encountering difficulties resolving a constructor with two instances of the same interface using Autofac in C# can refer to this query.

    public class MyClass : IMyClass { public MyClass(IService serviceA, IService serviceB) { // Constructor logic } }

    This code snippet defines a class MyClass with a constructor that takes two parameters of the same interface IService.

  9. "Autofac inject multiple implementations same interface C#"

    Description: This query addresses users trying to inject multiple implementations of the same interface into a constructor using Autofac in C#.

    builder.RegisterType<ImplementationA>().As<IService>(); builder.RegisterType<ImplementationB>().As<IService>();

    This code snippet registers two different implementations (ImplementationA and ImplementationB) for the IService interface.

  10. "C# Autofac resolve constructor with duplicate interface parameters"

    Description: Users looking to resolve a constructor with duplicate interface parameters using Autofac in C# can refer to this query.

    public class MyClass : IMyClass { public MyClass(IService serviceA, IService serviceB) { // Constructor logic } }

    This code snippet defines a class MyClass with a constructor that takes two parameters of the same interface IService.

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