How to resolve different services in different controllers?

Question

I have two MVC controllers.

Both controllers have an dependency on the IFileContainer interface.

In one controller I want resolve FsFileContainer and in second controller I want resolve FtpFileContainer.

Register:

    serviceCollection.AddTransient<IFileContainer, FsFileContainer>();
    serviceCollection.AddTransient<IFileContainer, FtpFileContainer>();

How to resolve container in this case?

Answer 1

The easiest way is to use a factory instead as the ASP.NET Core IoC Container doesn't support named dependencies or use a 3rd party IoC container which supports it.

public class FileContainerFactory : IFileContainerFactory 
{
    private readonly IServiceProvider provider;
    public class FileContainerFactory(IServiceProvider provider)
    {
        this.provider = provider;
    }

    public IFileContainer CreateFileSystemContainer() 
    {
        // resolve it via built in IoC
        return provider.GetService<FsFileContainer>();
    }

    public IFileContainer CreateFtpContainer() 
    {
        // resolve it via built in IoC
        return provider.GetService<FtpFileContainer>();
    }
}

Then inject the IFileContainerFactory into your controller.

An alternative is to mark your interfaces with a marker interface and register/inject these

// It defines no new methods or properties, just inherits it and acts as marker
public interface IFsFileContainer : IFileContainer {}
public interface IFtpFileContainer : IFileContainer {}

public class FsFileContainer : IFsFileContainer
{
    ...
}

in Startup.cs

services.AddTransient<IFsFileContainer, IFileContainer>();
services.AddTransient<IFtpFileContainer, IFileContainer>();