Error while validating the service descriptor 'ServiceType: MediatR.IRequestHandler

Question

I implement JwtService from IJwtService at the Infrastructure layer IJwtService declare at the Application layer and

I implement IdentityService from IIdentityService at the Infrastructure layer

I register both at infrastructure dependency injection like

services.AddTransient< IJwtService,JwtService>();
services.AddTransient<IIdentityService,IdentityService>();

Then I implement LoginQueryHandler implement from : IRequestHandler<LoginViewModel, LoginDto> within LoginQueryHandler() i inject IIdentityService and IJwtService

I register Mediator at Application Layer as this

services.AddMediatR(Assembly.GetExecutingAssembly());

using mediator I send a request to LoginQuery Handler

public async Task Login([FromBody] LoginViewModel model)
{

        return await Mediator.Send(model);
}

This is LoginQueryHandler Class

public class LoginViewModel: IRequest<LoginDto>
{
public string Email { get; set; }
public string Password { get; set; }


}
public class LoginQueryHandler : IRequestHandler<LoginViewModel, LoginDto>
{

private readonly IIdentityService _identityService;
private readonly IJwtService _jwtService;
public LoginQueryHandler(IIdentityService identityService,IJwtService jwtService)
{
    _identityService=identityService;
    _jwtService=jwtService;
    
}

public async Task<LoginDto> Handle(LoginViewModel request, CancellationToken cancellationToken)
{
    try
    {
        var user = await _identityService.FindByEmailAsync(request.Email);
       // codes....
        return new LoginDto();
    }
    catch (Exception ex)
    {
        throw ex;
    }
   
}
}

but it throws the following error

System.InvalidOperationException: Error while validating the service descriptor 'ServiceType: MediatR.IRequestHandler`2[Application.Login.Queries.LoginViewModel,Application.Login.Queries.LoginDto] Lifetime: Transient ImplementationType: Application.Login.Queries.LoginQueryHandler': Unable to resolve service for type 'TechneTravel.Infrastructure.Services.JwtService' while attempting to activate 'Newproject.Infrastructure.Identity.IdentityService'. ---> System.InvalidOperationException: Unable to resolve service for type 'Newproject.Infrastructure.Services.JwtService' while attempting to activate 'Newproject.Infrastructure.Identity.IdentityService'

Then I tried three ways to register Request Handler at the Application layer as bellow

services.AddTransient(typeof(IRequestHandler<LoginViewModel, LoginDto>), typeof(LoginQueryHandler));

 services.AddTransient<IRequestHandler<LoginViewModel, LoginDto>, LoginQueryHandler>();
 services.AddTransient(typeof(LoginQueryHandler));

but not solved

Answer 1

Based on your error message it seems that you are trying to resolve JwtService in your Newproject.Infrastructure.Identity.IdentityService but you have only interface registration:

services.AddTransient<IJwtService, JwtService>();

So either change your IdentityService to accept IJwtService instead of JwtService (I would say that it is far better option) or change/add registration to inject using concrete class:

services.AddTransient<JwtService>();