CODEWITHSUNDEEP
asp.net-mvcdependency-injectionninjectinversion-of-controlninject.web.mvc
Arnold Zahrneinder
Arnold Zahrneinder

Reputation: 5200

Property injection upon initializing object manually

When using Ninject property injection the following works only if the object is instantiated by the framework (not by developer in code) so that the injection works:

public class SomeController: Controller {
   [Inject]
   public DbContext db {get; set;}

 ...
}

However when the object has to be instantiated in the code by the developer the binding does not happen (I don't wanna say fail because it does not happen). 

public class DataProvision {
   [Inject]
   public DbContext db {get; set;}

   public List<T> GetList<T>() where T: class, new() {
       return db.Set<T>().toList();
   }
 ...
}

public class Test {
    public static void Test(){
        DataProvision dp = new DataProvision();
        var getValue = dp.GetList<Person>();
    }
}

Is it even supported by Ninject and if yes what is the solution.

Justification of why we are doing this: Switching between back-up databases and active DBs effortlessly in case emergency

Upvotes: 1

Views: 160

Answers (1)

StriplingWarrior
StriplingWarrior

Reputation: 156524

This is expected behavior. The DI framework has no opportunity to inject anything if you new up your own instances. If your code has access to the DI bindings, set up a kernel and use it to instantiate your class:

public class Test {
    public static void Test(){
        var kernel = new StandardKernel(new YourDiModule());
        DataProvision dp = kernel.Get<DataProvision>();
        var getValue = dp.GetList<Person>();
    }
}

Using the above strategy, you'll probably need to tweak your DI configuration a little so that your context gets disposed when you want it to. (Your web application is probably normally set up to dispose the context after each web request completes, and it doesn't look like your test code is set up to run in the same kind of environment.)

Otherwise, you'll need to manage the dependency injection by hand:

public class Test {
    public static void Test(){
        using (var context = new DbContext()) // or however you create contexts
        {
            DataProvision dp = new DataProvision();
            dp.db = context;
            var getValue = dp.GetList<Person>();
        }
    }
}

Upvotes: 2

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