Configuration .NET Core

Question

So I've been following this guide, but all examples are either accessing the options in the same method in which they were declared or in a controller. For the life of me, I can't figure out how to get it to work with any random class.

Here's my current code:

appsettings.json

{
  "Settings": {
    "GameServerVersion": 14
  },
  ....
}

Settings.cs

public class Settings
{
    public int GameServerVersion { get; set; }
}

Startup.cs

public Startup(IHostingEnvironment env)
{
    var builder = new ConfigurationBuilder()
        .SetBasePath(env.ContentRootPath)
        .AddJsonFile("appsettings.json", optional: false, reloadOnChange: true)
        .AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: true, reloadOnChange: true)
        .AddEnvironmentVariables();
    this.Configuration = builder.Build();
}

public IConfigurationRoot Configuration { get; }

// This method gets called by the runtime. Use this method to add services to the container.
public void ConfigureServices(IServiceCollection services)
{
    // Add framework services.
    services.AddMvc();
    services.AddCors();
    services.AddOptions();

    services.Configure<Settings>(this.Configuration.GetSection("Settings"));

    JobManager.StartAsync();
}

JobManager.cs

public class JobManager
{
    private static IScheduler scheduler;

    public static async void StartAsync()
    {
        // Quartz.NET jobs
        // Setup scheduler, register jobs, etc.
        // Trying to retrieve ```Settings.GameServerVersion``` to pass it to one of the jobs
    }
}

Now the guide suggests I should be using the following (applied to my example):

private readonly Settings settings;

public JobManager(IOptions<Settings> settingsAccessor)
{
    settings = settingsAccessor.Value;
}

And this is where I start to get lost. I understand I could just use the following, but I don't know what or how to pass the relevant parameter to the constructor.

JobManager jm = new JobManager(); // cannot use an empty constructor obviously
jm.StartAsync(); // no longer a static method

Any help or guidance would be much appreciated, as I'm still very new to C#.

You should register your JobManager in dependency injection container (services.AddSingleton or similar) and resolve it from there instead of manually constructing. — Evk
– Evk, Commented Aug 16, 2017 at 13:32
Could you maybe go into a bit more detail? I think I understand what you mean, but am rather unsure about the implementation — Chris Satchell
– Chris Satchell, Commented Aug 16, 2017 at 13:39

Evk · Accepted Answer · 2017-08-16 14:17:05Z

3

It's better to not perform any static initialization (like static RunAsync in your case) when you use dependency injection container. Instead, register JobManager itself (preferrably through interface) in container (assuming you pass IOptions though constructor as in your example):

services.AddSingleton<JobManager>();

Then, later, for example in Configure method in your Startup class, resolve it and start:

public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory) {
    var jm = app.ApplicationServices.GetService<JobManager>();
    jm.StartAsync();
    // etc
}

If you will need to use JobManager in any controller - just pass it though constructor - it will be resolved automatically.

answered Aug 16, 2017 at 14:17

Evk

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2 Comments

Chris Satchell Over a year ago

Sir, you are a true hero, thank you very much. The GetService part was the missing link. Is it possible to get this to work with IOptionsSnapshot as well?

Evk Over a year ago

@ChrisSatchell IOptionsSnapshot is no different. You register some stuff in dependency injection container (or in case of IOptions or IOptionsSnapshot - framework does that) and you can pass that as arguments to constructor of any other stuff registered in the same container.

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