connection string injection - ninject

Question

I am trying to learn Ninject and started with what I thought is very simple thing. Can't make it work. Obviously, I am missing something basic.
So, I have this little console application that listens for WCF calls on a certain port and saves data that come via WCF to a database. There are 3 projects in the solution: 1. data access library, 2. WCF stuff and 3. console acting as a host. Ninject is not used yet. So the dependencies between projects are like this: 3 -> 2 -> 1
I want to start with injecting connection string that console host takes from its config into data access library. Googling for ninjection of connection string brought some examples, but they are not complete.
One of the examples suggested to bind in the host's Main() like this:
static void Main(string[] args)
{
new StandardKernel().Bind<ConnectionStringProvider>().ToConstant(
new ConnectionStringProvider { ConnectionString = Config.ConnectionString });
}
where ConnectionStrinProvider is a simple class that contains only one property ConnectionString. What I can't figure out is how do I instantiate ConnectionStrinProvider in the data access library. I tried
var csprovider = new StandardKernel().Get<ConnectionStringProvider>();
it doesn't work - meaning that it returns new instance of the provider instead of the one that was created during binding. I also tried to add .InSingletonScope() to the binding, with the same result.

Answer 1

You need to keep a reference to the kernel you set up. It doesn't work if you instantiate it every time.
public static IKernel Ninject {get; private set;}
static void Main(string[] args)
{
Ninject = new StandardKernel()
Ninject.Bind<ConnectionStringProvider>().ToConstant(
new ConnectionStringProvider { ConnectionString = Config.ConnectionString });
}
On the consummer side, you can call the Ninject static property on your main.
Obvious note aside: this is sample code, on production code you may want to make a better design for that global static variable.

Answer 2

The kernel is what keeps track of all the bindings for you. However, you are creating a new instance each time. That won't work. Instead, create the kernel and then store it off (here I'm storing it off in a local variable, but you'd probably want to store it in a field in some class):
var connectionStringProvider = new ConnectionStringProvider { ConnectionString = Config.ConnectionString };
var kernel = new StandardKernel().Bind<ConnectionStringProvider>().ToConstant(connectionStringProvider);
Now obtain instances by accessing the existing kernel.
var csprovider = kernel.Get<ConnectionStringProvider>();
That being said, using it in this fashion is the wrong way to go about it, as this pattern is known as a service locator pattern, which is the antitheses of dependency injection. Generally speaking, you have a top-level class (for example, your application class with the Main method) that is either obtained via Kernel.Get or injected via Kernel.Inject, and all other dependencies are injected normally through constructors or [Inject]'ed properties.
Also, there are usually plugins available for most situations so that you don't have to instantiate the kernel yourself. However, I'm not aware of one for console apps.