ASP.NET 5 - Using a Configuration Setting

Question

I am playing with ASP.NET 5. I am trying to understand the new configuration model. I have read several articles. However, I am still unsuccessful in loading a configuration setting. My config.json file looks like this:

{
    "App" : {
        "Info" : {
            "Version":"1.0.0",
            "ReleaseDate":"03-15-2015"
        }
    }
}

My Startup.cs file looks like this:

public class Startup
{
    public IConfiguration Configuration { get; private set; }

    public Startup()
    {
        Configuration = new Configuration()
            .AddJsonFile("config.json");
    }

    public void ConfigureServices(IServiceCollection services)
    {
        services.AddMvc();
    }

    public void Configure(IApplicationBuilder app)
    {
        app.UseErrorPage();
        app.UseMvc(routes =>
        {
            routes.MapRoute("default", "{controller}/{action}/{id}", defaults: new { controller = "Home", action = "Index" });
        });

        app.UseMvc();
        app.UseWelcomePage();
    }
}

In one of my controllers, I have the following

MyController.cs

using System;
using Microsoft.AspNet.Mvc;

namespace MyOrg.MyApp
{
    public class MyController : Controller
    {
        [HttpGet()]
        public ActionResult Index()
        {
            var version = Configuration.Get("App:Info:Version");
            return new HttpStatusCodeResult(200);
        }
    }
}

When I start the app, I get an error that says:

error CS0103: The name 'Configuration' does not exist in the current context
   at Microsoft.Framework.Runtime.Roslyn.RoslynProjectReference.Load(IAssemblyLo
adContext loadContext)
   at Microsoft.Framework.Runtime.Loader.ProjectAssemblyLoader.Load(String name,
 IAssemblyLoadContext loadContext)
   at Microsoft.Framework.Runtime.Loader.ProjectAssemblyLoader.Load(String name)

   at kre.host.LoaderContainer.Load(String name)
   at kre.hosting.RuntimeBootstrapper.<>c__DisplayClass6_0.<ExecuteAsync>b__4(As
semblyName assemblyName)
   at kre.hosting.RuntimeBootstrapper.<>c__DisplayClass6_0.<ExecuteAsync>b__7(Ob
ject sender, ResolveEventArgs a)
   at System.AppDomain.OnAssemblyResolveEvent(RuntimeAssembly assembly, String assemblyFullName)

What am I doing wrong? I feel like I've followed the examples I've seen. Yet, I can figure out what I'm doing wrong.

Answer 1

As of Beta 5 the accepted answer is no longer correct. There is no longer a Get method on IConfiguration. Also the way of constructing the configuration object is also changed.

The following code works on Beta 7:

// showing using statements here since this is new from Beta 5
using Microsoft.Dnx.Runtime; // renamed was Microsoft.Framework.Runtime
using Microsoft.Framework.Configuration; // renamed was Microsoft.Framework.ConfigurationModel
// other using statements here

// Startup constructor. Note: now takes IApplicationEnvironment
// this is required in order to get base path
public Startup(IHostingEnvironment env, IApplicationEnvironment appEnv)
{
        // Setup configuration sources.
        var builder = new ConfigurationBuilder(appEnv.ApplicationBasePath)
            .AddJsonFile("config.json")
            .AddJsonFile("dbconfig.json")
            .AddEnvironmentVariables();

        Configuration = builder.Build();
}

// property to hold configuration object created in constructor
public IConfiguration Configuration { get; set; }

public void ConfigureServices(IServiceCollection services)
{
   // this will bind to an IOptions<AppSettings> instance
   // where AppSettings is a class you define that has a set of 
   // properties that match your configuration section loaded from the 
   // json file
   services.Configure<AppSettings>(Configuration.GetSection("AppSettings"));

   // here I am loading a connection string from a json file and passing into an
   // new EF 6.x DB Context class
   services.AddInstance<TalentAgencyContainer>(new TalentAgencyContainer(Configuration["ConnectionStrings:TalentAgencyContainer"]));

        // Add MVC services to the services container.
        services.AddMvc();

}

Answer 2

Clearly you want to access Configuration property in your Startup class. And the error method says it doesn't know what Configuration is. So you need a using statement or a fully qualified name. Also, you should avoid naming things the same thing as stuff found in the framework. Your Startup class has a Configuration property, but it also tries to use the Configuration class from Microsoft.Framework.ConfigurationModel. How confusing is that?

Your Configure() method in Startup needs a using statement or fully qualified name so it knows what the Configuration class is.

using Microsoft.Framework.ConfigurationModel; //at the top of your class
Configuration = new Configuration(); //later in the code, we can access without fully qualifying name

or

Configuration = new Microsoft.Framework.ConfigurationModel.Configuration();

In your controller, you may have a similar issue. Replace MyOrg.MyApp.Startup in the example below with whatever the namespace is for your Startup class.

using MyOrg.MyApp.Startup //at the top of your class
Startup.Configuration.Get("App:Info:Version"); //later in the code, we can access without fully qualifying name

or

 MyOrg.MyApp.Startup.Startup.Configuration.Get("App:Info:Version");

---

Better way of doing things

That should be enough to get you started. However, accessing the Startup class to retrieve your configuration isn't ideal, because now your controller's action methods depend on having the Startup class there. That's not very unit testable. Ideally your controllers should be isolated from each other. You should define some sort of interface to hold the configuration info you want, then have the controller depend on that interface. When you're in your site, you'll respond with a class specific to the site's configuration. When unit testing, you can have tight control over the test values by using a different class.

interface ISiteConfig
{
    string Version {get; set;}
    DateTime ReleaseDate {get; set;}
}

public class SiteConfig : ISiteConfig
{
    public string Version {get; set;}
    public DateTime ReleaseDate {get; set;}

    public SiteConfig()
    {
        var c = new Configuration()
        .AddJsonFile("config.json");
        Version = c.Get("App:Info:Version");
        ReleaseDate = c.Get("App:Info:ReleaseDate"); //may need to parse here
    }
}

public class TestConfig : ISiteConfig
{
    public string Version {get; set;}
    public DateTime ReleaseDate {get; set;}

    public TestConfig(string version, DateTime releaseDate)
    {
         Version = version;
         ReleaseDate = releaseDate;
    }
}

Then you'd use Dependency Injection to inject instances of your configuration into the Controller.

public class MyController : Controller
{
    private readonly ISiteConfig Config;

    public MyController(ISiteConfig config)
    {
        Config = config;
    }

    [HttpGet()]
    public HttpStatusCodeResult Index()
    {
        var version = Config.Version;
        return new HttpStatusCodeResult(200);
    }
}


public class Startup
{
    public void Configure(IBuilder app)
    {
        ...
        app.UseServices(services =>
        {
            ...
            // Set up the dependencies
            services.AddTransient<ISiteConfig, SiteConfig>();
            ...
        });
        ...
    }
}

Now you can more easily unit test your action methods, because your unit tests can use the TestConfig class while the site can use the SiteConfig class. And also if you want to change how your configuration is done, you don't have to replace strings in a bunch of different places. You'll have one class where you do so, the rest is strongly typed and easy to change without blowing up your application.

Your unit test might look like this:

//Arrange
var testConfig = new TestConfig("1.0", DateTime.Now );
var controller = new MyController(testConfig );  

//Act
var response = controller.Index();

//Assert
Assert.AreEqual(200, response.StatusCode);