ASP.NET Core 6: implementing Null Reference handling in Dependency Injection for Scoped Services
I've tried everything I can think of but Could someone explain I'm having trouble with a `NullReferenceException` when trying to inject a scoped service into a controller in my ASP.NET Core 6 application..... I've defined a class `UserService` that implements an `IUserService` interface, and I'm registering it in the `Startup.cs` file as a scoped service. However, when I try to use it in my controller, I get the following behavior: `Object reference not set to an instance of an object`. Here's how I set up my service registration in `Startup.cs`: ```csharp public void ConfigureServices(IServiceCollection services) { services.AddScoped<IUserService, UserService>(); services.AddControllers(); } ``` And in my `UserController`, I have the following constructor: ```csharp public class UserController : ControllerBase { private readonly IUserService _userService; public UserController(IUserService userService) { _userService = userService; } } ``` I checked that `UserService` is not null in the constructor, but when I try to call any method on `_userService`, it throws the exception. I also verified that the `UserService` class looks like this: ```csharp public class UserService : IUserService { public string GetUserName(int id) { // Simulated database call return "User" + id; } } ``` Interestingly, if I change the registration to `AddSingleton`, the behavior goes away, but I know that’s not the right scope for my use case. I’ve also checked for circular references in my dependencies and ensured that everything is registered properly. Any thoughts on why this might be happening? Am I missing something regarding the lifetime of my services or how ASP.NET Core manages dependency injection? For reference, this is a production service. What's the best practice here?