Object reference not set to an instance of an object, Interface

Question

I know that this is one of the most encountered error but I am really struggling to get around it. i have a property on my Controller: private readonly ISelectListFactory _selectFactory; and a method that called to populate the viewbag private void PopulateLists() { var continent = _selectFactory.GetItems(); } and the interface

public interface ISelectListFactory
{
    IEnumerable<SelectListItem> GetItems();

}

and in the controller constructor I have the following:

public LocationController(ISelectListFactory selectFactory)
    {
        _selectFactory = selectFactory;
     }

but I am getting this error Object reference not set to an instance of an object and not sure how to overcome it.

Regards

Do you have a line of code where an instance of an object gets created and placed into _selectFactory? — David Tansey
– David Tansey, Commented Aug 11, 2013 at 17:16
@DavidTansey there is a method that implement the ISelectListFactory where the GetItems methods is defined, but strange enough if I put a breakpoint on GetItems, I don't get there and this is strange to me — Jack M
– Jack M, Commented Aug 11, 2013 at 17:44
@DavidTansey: you are right mate thanks was blinded by the readonly property.Cheers — Jack M
– Jack M, Commented Aug 11, 2013 at 17:59

Darin Dimitrov · Accepted Answer · 2013-08-11 17:18:57Z

1

Make sure you have instantiated this _selectFactory variable somewhere. Like for example:

_selectFactory = new SomeConcreteSelectListFactory();

or if you are using dependency injection you might configure your DI framework to inject it into the constructor:

public class HomeController: Controller
{
    private readonly ISelectListFactory _selectFactory;
    public HomeController(ISelectListFactory selectFactory)
    {
        _selectFactory = selectFactory;
    }

    ... some controller actions where you could use the _selectFactory field
}

answered Aug 11, 2013 at 17:18

Darin Dimitrov

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