Ninject bindings 101

Question

Newbie Ninject question klaxxon.

I have the following classes and interfaces which describe a dependency I need to inject, and a depender into which a concrete instance of the dependency needs to be injected.

public interface IDependency { }

public class FooDependency : IDependency { }

public class Depender
{
    [Inject]
    public IDependency Dependency { get; set; }

    public bool DependencyIsNull()
    {
        return Dependency == null;
    }
}

I have setup my bindings with a NinjectModule instance, like so.

public class Bindings : NinjectModule
{
    public override void Load()
    {
        Bind<IDependency>().To<FooDependency>();
    }
}

And here's a unit test method which asserts that the dependency has been injected into the depender.

[TestMethod]
public void TestMethod1()
{
   var kernel = new StandardKernel(new Bindings());
   var bar = new Depender();
   Assert.IsFalse(bar.DependencyIsNull());
}

I'm clearly doing something fundamentally wrong, as I would have expected the test to pass, but it doesn't.

Answer 1

Your object isn't created by your kernel. Everything needs to be created by the kernel to have dependencies injected:

// option a (recommended)
var kernel = new StandardKernel(new Bindings());
var bar = kernel.Get<IDependency>();
Assert.IsFalse(bar.DependencyIsNull());

// option b (not recommended.. but do-able)
var kernel = new StandardKernel(new Bindings());
var bar = new Depender();
kernel.Inject(bar); // injects after the fact
Assert.IsFalse(bar.DependencyIsNull());

Also, you should have that DependencyIsNull method in your interface:

public interface IDependency {
    bool DependencyIsNull();
}