Ninject property injection returns null

Question

I'm sure I'm doing something stupid but this is what we're here for!

I've got a WinForms app with the following code:

static void Main()
{
    IKernel kernel = new StandardKernel(new MyModule());
    TestInterface test = kernel.Get<TestInterface>();
}

For the Module.Load() event:

Bind<TestClass>().ToSelf().InSingletonScope();
Bind<TestInterface>().To<TestClass>();

At this point test in the Main() method is the proper object I'm expecting.

In a form later on, I'm using property injection:

[Inject]
TestInterface test {get;set;}

And once the form is loaded, trying to work with test, but it's a null object.

Thoughts?

Answer 1

Make sure you call Inject() on the IKernel instance and pass in an instance of your form. This will ensure all dependencies are properly injected. For example...

[Inject]
TestInterface Test { get; set; }

private void Form_Load(object sender, EventArgs e)
{            
    IKernel kernel = ... // Get an instance of IKernel
    kernel.Inject(this);

    // Your form dependencies have now been injected and the 
    // Test property is ready to use
}

Answer 2

Instead of doing

var form = new MainForm()

...

class MainForm
{
    MainForm()
    {
        GlobalKernel.Inject(this)

....

You want to be doing:

var form = Kernel.Get<MainForm>()

Which obviates the need for the explicit Inject (and allows you to do constructor injection).

I dont know of any WinForms (or WPF) samples for Ninject (but it'd be a good question to ask and/or stick a bounty on -- IIRC one came up recently)

See also:

http://stackoverflow.com/questions/693690/ioc-di-framworks-with-smart-client-winform-apps-how-should-i-approach-this

http://stackoverflow.com/questions/3493932/what-is-the-best-practice-for-winforms-dialogs-with-ninject