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c#.netasp.net-coreloggingilogger

How to provide ILogger<ClassName> instance in new class object from controller in .net core?


As giving null it gives Value cannot be null. (Parameter 'logger') error. Even if instance of model is given it still stays null

 public class MyController : Controller
    {
            public MyController(ILogger<MyController> logger)
            {
              logger.LogInformation("Log Testing");
            }

            public ActionResult List()
            {
                int Id = 5;
                MyModel model = new MyModel(null);
                model.GetItem(Id);
                return View("List", model);
            }
    }

public class MyModal:BaseModel
{
    private readonly ILogger<MyModal> _logger;
    public MyModel(ILogger<MyModel> logger) 
        {
           this._logger = logger;
        }

    public MyModel GetItem (Int Id)
    {
      try
      {
        //My Code
      }
      catch(Exception e){
       _logger.LogError(e.Message);
      }
    }
}

As per the suggestion i edited my question


Solution

  • As suggested in the comments:

    1. Inject ILoggerFactory into MyController and store it in a field variable (e.g. _loggerFactory).
    2. Use the factory to construct a logger for MyModel in your List method: ILogger<MyModel> modelLogger = _loggerFactory.CreateLogger<MyModel>();
    3. Pass it into the MyModel constructor: MyModel model = new MyModel(modelLogger);

    Example:

    public class MyController
    {
        private readonly ILogger _logger;
        private readonly ILoggerFactory _loggerFactory;
        
        public MyController(ILogger<MyController> logger, ILoggerFactory loggerFactory)
        {
            _logger = logger;
            _loggerFactory = loggerFactory;
        }
    
        public ActionResult List()
        {
            int Id = 5;
            ILogger<MyModel> modelLogger = _loggerFactory.CreateLogger<MyModel>();
            MyModel model = new MyModel(modelLogger);
            model.GetItem(Id);
            return View("List", model);
        }
    }
    

    Try it online