Unable to resolve service for type in .NET Core

I get this error:

> Unable to resolve service for type

I am using are unit of work repository project, on .NET Core. I had a services on another layer, but I changed to TestServices, then I created a Services layer where are FlightService and IFlightService.

Program

builder.Services.AddDbContext<DataContext>(options =>
    options.UseSqlServer(builder.Configuration
    .GetConnectionString("ConnectionString")));

builder.Services.AddControllers().AddJsonOptions(x =>
                x.JsonSerializerOptions.ReferenceHandler = ReferenceHandler.IgnoreCycles);

builder.Services.AddTransient<IUnitOfWork, UnitOfWork>();

builder.Services.AddScoped<IFlightRepository, FlightRepository>();

builder.Services.AddControllers();

FlightController:

[ApiController]
[Route("Api")]
public class FlightController : Controller
{
        private readonly ILogger<SearchFlightsController> _logger;        
        private readonly IUnitOfWork unitOfWork;
        public readonly IFlightService _flightService;

        public FlightController(ILogger<SearchFlightsController> logger,
            IUnitOfWork unitOfWork,
            IFlightService flightService)
        {
            _logger = logger;            
            this.unitOfWork = unitOfWork;
            _flightService = flightService;
        }

        [HttpGet("GetFlightById/{flightId}")]
        public async Task<IActionResult> GetFlightById(int flightId)
        {
            var details = await _flightService.GetFlightById(flightId);

            if (details != null)
            {
                return Ok(details);
            }
            else
            {
                return BadRequest();
            }
        }
}

Error

> System.InvalidOperationException: Unable to resolve service for type 'Services.Interfaces.IFlightService' while attempting to activate 'NewShore.Controllers.FlightController'.
>
> at Microsoft.Extensions.DependencyInjection.ActivatorUtilities.GetService(IServiceProvider sp, Type type, Type requiredBy, Boolean isDefaultParameterRequired)
> at lambda_method4(Closure, IServiceProvider, Object[])
> at Microsoft.AspNetCore.Mvc.Controllers.ControllerFactoryProvider.<>c__DisplayClass6_0.<CreateControllerFactory>g__CreateController|0(ControllerContext controllerContext)
> at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
> at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.InvokeInnerFilterAsync()
> --- End of stack trace from previous location ---
> at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeFilterPipelineAsync>g__Awaited|20_0(ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
> at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeAsync>g__Awaited|17_0(ResourceInvoker invoker, Task task, IDisposable scope)
> at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeAsync>g__Awaited|17_0(ResourceInvoker invoker, Task task, IDisposable scope)
> at Microsoft.AspNetCore.Routing.EndpointMiddleware.<Invoke>g__AwaitRequestTask|6_0(Endpoint endpoint, Task requestTask, ILogger logger)
> at Microsoft.AspNetCore.Authorization.AuthorizationMiddleware.Invoke(HttpContext context)
> at Swashbuckle.AspNetCore.SwaggerUI.SwaggerUIMiddleware.Invoke(HttpContext httpContext)
> at Swashbuckle.AspNetCore.Swagger.SwaggerMiddleware.Invoke(HttpContext httpContext, ISwaggerProvider swaggerProvider)
> at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddlewareImpl.Invoke(HttpContext context)

I read some posts, I tried changing to AddScoped both, AddTransient for IFlightRepository. I saw the order or the commands on Program.cs but everything seems ok.

Can you please correct me?

You injected IFlightService into FlightController, but not registered this dependency. Error message tells you that dependency in FlightController cannot be resolved.

Add this line to Program.cs

builder.Services.AddTransient<IFlightService, FligtService>();