ASP.NET Core 3.1 injecting array of objects from appsettings.json into an injected service

Question

I'm trying to inject a couple email accounts that I have in appsettings.json into an email service.

EDIT: My EmailRepository.cs needs a DbContextinjected as well. I used @Nkosi 's answer, which worked without needing a DbContext. I'm planning on using DbContextPool in production, so how do I pull one of those out in my ConfigureServices method?

appsettings.json:

"SanSenders": [
  {
    "Host": "mail.theFourSeasons.com",
    "FromName": "The Four Seasons",
    "IsNoReply": true,
    "IsSssl": true,
    "Password": "tooGoodToBeTrue",
    "Port": 465,
    "Username": "[email protected]"
  },

  {
    "Host": "mail.theFourSeasons.com",
    "FromName": "Franki",
    "IsNoReply": false,
    "IsSssl": true,
    "Password": "cantTakeMyEyesOffYou",
    "Port": 465,
    "Username": "[email protected]"
  }
]

SanSender.cs:

public class SanSender
{
    public string FromName { get; set; }
    public string Host { get; set; }
    public bool IsNoReply { get; set; }
    public bool IsSsl { get; set; }
    public string Password { get; set; }
    public int Port { get; set; }
    public string Username { get; set; }

    public async Task<bool> SendEmailAsync(
        string toAddress, string subject, string htmlMessage)
    {
        throw new NotImplementedException();
    }
}

EmailRepository.cs:

public class EmailRepository
{
    public IEnumerable<SanSender> SanSenders { get; set; }

    //Edit: I need a DbContext injected as well.
    public EmailRepository(ApplicationDbContext applicationDbContext,  
        IEnumerable<SanSender> sanSenders)
    {
         SanSenders = sanSenders;
    }
}

Startup.cs:

public void ConfigureServices(IServiceCollection services)
{
    services.Configure<List<SanSender>>((settings) =>
    {
        Configuration.GetSection("SanSenders").Bind(settings);
    });

    services.AddScoped<EmailRepository>();

    services.AddControllersWithViews();
}

The Controller:

public class HomeController : Controller
{
    public HomeController(
        IOptions<List<SanSender>> optionsSanSenders, EmailRepository emailService)
    {
    }

    public IActionResult Index()
    {
        return View();
    }
}

In the controller I added IOptions<List<SanSender>> optionsSanSenders and I can get access to them there, but EmailService.cs is in a class library and I would prefer to not add unnecessary dependencies to it.

The EmailService does have IEnumerable<SanSender> SanSenders, but it has a zero length/count.

What am I doing wrong?

Nkosi · Accepted Answer · 2020-04-01 21:26:47Z

Change the approach.

public class SanSenderOptions {
     public List<SanSender> SanSenders { get; set; }
}

Extract the settings from configuration and then register them where needed

public void ConfigureServices(IServiceCollection services) {
    SanSender[] senders = Configuration.GetSection("SanSenders").Get<SanSender[]>();

    services.Configure<SanSenderOptions>(options => {
        options.SanSenders = senders.ToList();
    });

    services.AddScoped<EmailRepository>(sp => 
        new EmailRepository(sp.GetRequiredService<ApplicationDbContext>(), senders));

    services.AddControllersWithViews();
}

The repository will get the senders injected being resolved.

The controller should be refactored to get the configured options.

public class HomeController : Controller {
    public HomeController(IOptions<SanSenderOptions>> optionsSanSenders, 
          EmailRepository emailService) {
        var senders = options.Value.SanSenders; //<--
    }

    public IActionResult Index() {
        return View();
    }

}

Reference Configuration in ASP.NET Core

Reference Options pattern in ASP.NET Core

Ugh, simplified my code for easier reading. Problem is, my EmailRepository needs a DbContext injected as well. And I'll be using DbContextPool in production, so don't want to new up an instance in configure services. Gonna update my question.
@MichaelTranchida updated answer. I also assume you registered the DbContext since it was not shown in the simplified example you provided.
Will this approach respect reloadOnChange for the json file?

ViRuSTriNiTy · Accepted Answer · 2023-02-28 08:36:27Z

2

Introducing an additional configuration level as mentioned in answer of Nkosi is not needed (anymore?) in .NET 6.

You can use IOptions<List<SanSender>> to inject and fetch the configuration in classes.

Additionally I would recommend to use binding to tell how the configuration is fetched like

services.Configure<List<SanSender>>(
    options => Configuration.Bind("SanSenders", options));

answered Feb 28, 2023 at 8:36

ViRuSTriNiTy

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