ASP.Net Core MVC Dependency Injection not working

Question

I am trying to inject a interface into to my HomeController and I am getting this error:

InvalidOperationException: Unable to resolve service for type 'Microsoft.Extensions.Configuration.IConfiguration' while attempting to activate

My Startup class is as follows:

public Startup(IApplicationEnvironment appEnv)
{
    var builder = new ConfigurationBuilder()
        .SetBasePath(appEnv.ApplicationBasePath)
        .AddEnvironmentVariables()
        .AddJsonFile("appsettings.json");
    Configuration = builder.Build();
}

public IConfigurationRoot Configuration { get; set; }

public void ConfigureServices(IServiceCollection services)
{
    // Add framework services.
    services.AddApplicationInsightsTelemetry(Configuration);

    services.AddEntityFramework()
        .AddSqlServer()
        .AddDbContext<ApplicationDbContext>(options => options
            .UseSqlServer(Configuration["Data:DefaultConnection:ConnectionString"]));

    services.AddIdentity<ApplicationUser, IdentityRole>()
        .AddEntityFrameworkStores<ApplicationDbContext>()
        .AddDefaultTokenProviders();

    services.AddMvc();
    services.AddSingleton(provider => Configuration);

    // Add application services.
    services.AddTransient<IEmailSender, AuthMessageSender>();
    services.AddTransient<ISmsSender, AuthMessageSender>();
}

public void Configure(
    IApplicationBuilder app, 
    IHostingEnvironment env, 
    ILoggerFactory loggerFactory)
{
    loggerFactory.AddConsole(Configuration.GetSection("Logging"));
    loggerFactory.AddDebug();

    app.UseApplicationInsightsRequestTelemetry();

    if (env.IsDevelopment())
    {
        app.UseBrowserLink();
        app.UseDeveloperExceptionPage();
        app.UseDatabaseErrorPage();
    }
    else
    {
        app.UseExceptionHandler("/Home/Error");

        try
        {
            using (var serviceScope = app.ApplicationServices
                .GetRequiredService<IServiceScopeFactory>()
                .CreateScope())
            {
                serviceScope.ServiceProvider
                        .GetService<ApplicationDbContext>()
                        .Database.Migrate();
            }
        }
        catch { }
    }

    app.UseIISPlatformHandler(options => options.AuthenticationDescriptions.Clear());

    app.UseApplicationInsightsExceptionTelemetry();
    app.UseStaticFiles();
    app.UseIdentity();

    app.UseMvc(routes =>
    {
        routes.MapRoute(
            name: "default",
            template: "{controller=Home}/{action=Index}/{id?}");
    });

    app.Run((async (context) =>
    {
        await context.Response.WriteAsync("Error");
    }));
}

and my HomeController constructor is:

public HomeController(IConfiguration configuration, IEmailSender mailService)
{
    _mailService = mailService;
    _to = configuration["emailAddress.Support"];
}

Please tell me where I am mistaken.

Microsoft.Extensions.DependencyInjection.ServiceLookup.Service.PopulateCallSites(ServiceProvider provider, ISet`1 callSiteChain, ParameterInfo[] parameters, Boolean throwIfCallSiteNotFound)

I would recommend isolating your Configuration from your Controller by creating a POCO to store whatever configuration details you want passed, and injecting that instead. — steve v
– steve v, Commented Apr 22, 2016 at 19:53
The similar error can happen if constructor has object as a parameter, but service configured as interface stackoverflow.com/questions/40900414/… — Michael Freidgeim
– Michael Freidgeim, Commented Jan 28, 2018 at 6:50

Will Ray · Accepted Answer · 2016-04-22 20:22:59Z

36

Try injecting it as an IConfigurationRoot instead of IConfiguration:

 public HomeController(IConfigurationRoot configuration
    , IEmailSender mailService)
{
    _mailService = mailService;
    _to = configuration["emailAddress.Support"];
}

In this case, the line

services.AddSingleton(provider => Configuration);

is equivalent to

services.AddSingleton<IConfigurationRoot>(provider => Configuration);

because the Configuration property on the class is declared as such, and injection will be done by matching whatever type it was registered as. We can replicate this pretty easily, which might make it clearer:

public interface IParent { }

public interface IChild : IParent { }

public class ConfigurationTester : IChild { }

public void ConfigureServices(IServiceCollection services)
{
    // Add framework services.
    services.AddMvc();

    IChild example = new ConfigurationTester();
    services.AddSingleton(provider => example);
}

public class HomeController : Controller
{
    public HomeController(IParent configuration)
    {
        // this will blow up
    }
}

However

As stephen.vakil mentioned in the comments, it would be better to load your configuration file into a class, and then inject that class into controllers as needed. That would look something like this:

services.Configure<AppSettings>(Configuration.GetSection("AppSettings"));

You can grab these configurations with the IOptions interface:

public HomeController(IOptions<AppSettings> appSettings)

edited Apr 22, 2016 at 20:22

answered Apr 22, 2016 at 19:29

Will Ray

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4 Comments

steve v Over a year ago

Why? I do not do this in my code and it still works fine. And it is not done in this order in the docs: docs.asp.net/en/latest/fundamentals/dependency-injection.html

Will Ray Over a year ago

@stephen.vakil You're right, I was totally wrong on that detail. Thanks for the link! I have updated my answer, Jam.

JamTay317 Over a year ago

That was it! can you explain what the difference is?

Eilon Over a year ago

Inject it as an IConfiguration for greater flexibility.

Michael Freidgeim · Accepted Answer · 2017-11-14 07:04:18Z

9

In Core 2.0 it's recommended to use IConfiguration instead of IConfigurationRoot

public Startup(IConfiguration configuration)
{
    Configuration = configuration;
}

public IConfiguration Configuration { get; }

from https://learn.microsoft.com/en-us/aspnet/core/migration/1x-to-2x/#add-configuration-providers

answered Nov 14, 2017 at 7:04

Michael Freidgeim

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Comments

Roman Marusyk · Accepted Answer · 2017-12-07 21:11:47Z

2

When moving a project from .Net Core 1.x to 2.0, change all IConfigurationRoot to IConfiguration

edited Dec 7, 2017 at 21:11

Roman Marusyk

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answered Nov 15, 2017 at 20:21

Christian Esqueda

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