Unable to resolve service for type while attempting to activate
Solution 1
For the Dependency Injection framework to resolve IRepository
, it must first be registered with the container. For example, in ConfigureServices
, add the following:
services.AddScoped<IRepository, MemoryRepository>();
For .NET 6+, which uses the new hosting model by default, add the following in Program.cs instead:
builder.Services.AddScoped<IRepository, MemoryRepository>();
AddScoped
is just one example of a service lifetime:
For web applications, a scoped lifetime indicates that services are created once per client request (connection).
See the docs for more information on Dependency Injection in ASP.NET Core.
Solution 2
We are getting this error in Entity frame work core database first approach. I followed below steps and error got resolved
Step 1: Check Your context class constructor should be like this
public partial class ZPHSContext : DbContext
{
public ZPHSContext(DbContextOptions<ZPHSContext> dbContextOptions)
: base(dbContextOptions)
{
}
}
Step 2: In Startup file
public void ConfigureServices(IServiceCollection services)
{
services.AddMvc();
services.AddDbContext<ZPHSContext>(options =>
options.UseSqlServer(
Configuration.GetConnectionString("BloggingDatabase")));
}
Step 3: Connection string in appsettings
"ConnectionStrings": {
"BloggingDatabase": "Server=****;Database=ZPHSS;Trusted_Connection=True;"
}
Step 4: Remove default code in OnConfiguring method in context class
protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
}
Solution 3
Other answers are CORRECT, however I was spinning up a new asp.net core 2.1.x project and got this error.
Ended up being a typo by ME.
So in my Controller instead of Correctly using the Interface like this
public HomeController(IApplicationRepository applicationRepository)
{
_applicationRepository = applicationRepository;
}
My typo had me using ApplicationRepository
instead of its interface IApplicationRepository
Notice below, and so with NO ERRORS spotting the missing "I" was fun :/
public HomeController(IApplicationRepository applicationRepository)
{
_applicationRepository = applicationRepository;
}
Thus the controller was not resolving the DI...
Solution 4
A method like this needs to be added to your Startup
:
// This method gets called by the runtime. Use this method to add services to the container.
public void ConfigureServices(IServiceCollection services)
{
//...
// Add application services.
services.AddTransient<IRepository, MemoryRepository>();
//..
}
Services should be registered before used.
UPDATE:
If you do not want to use DI on your application, just create and instance of MemoryRepository
on the constructor of HomeController
, like this:
public class HomeController : Controller
{
private IRepository repository;
public HomeController()
{
repository = new MemoryRepository();
}
public IActionResult Index()
{
return View(repository.Cities);
}
}
Solution 5
This may not be helpful for your code sample but in my case the same error was a result of a circular dependency.
Vojislav Kovacevic
Updated on July 09, 2022Comments
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Vojislav Kovacevic almost 2 years
In my ASP.NET Core application, I get the following error:
InvalidOperationException: Unable to resolve service for type 'Cities.Models.IRepository' while attempting to activate 'Cities.Controllers.HomeController'.
I the
HomeController
I am trying to pass theCities
getter to the view like so:public class HomeController : Controller { private readonly IRepository repository; public HomeController(IRepository repo) => repository = repo; public IActionResult Index() => View(repository.Cities); }
I have one file
Repository.cs
that contains an interface and its implementation like so:public interface IRepository { IEnumerable<City> Cities { get; } void AddCity(City newCity); } public class MemoryRepository : IRepository { private readonly List<City> cities = new List<City>(); public IEnumerable<City> Cities => cities; public void AddCity(City newCity) => cities.Add(newCity); }
My
Startup
class contains the default-generated code from the template. I have made any changes:public class Startup { public Startup(IConfiguration configuration) { Configuration = configuration; } public IConfiguration Configuration { get; } public void ConfigureServices(IServiceCollection services) { services.AddControllersWithViews(); } public void Configure(IApplicationBuilder app, IWebHostEnvironment env) { ... } }
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Vojislav Kovacevic over 6 yearsHow could my existing code be modified to work without using DI?
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sezmeralda over 2 yearsI ... I can't believe this was my problem. Exactly my problem. So much pain... Thank you!
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Merna Mustafa over 2 yearsNo Way! this was my problem too!
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qqtf almost 2 yearsusing a singleton, I don't think that is a default solution, AddScoped makes more sense