What's the difference between .ToConstructor and .ToMethod in Ninject 3?

c# ninject
Shaddix picture Shaddix · Jan 8, 2012 · Viewed 9.4k times · Source

In Ninject3 there's a new .ToConstructor feature.

As described, it helps to strongly-type constructor arguments like:

Bind<IMyService>().ToConstructor(
    ctorArg => new MyService(ctorArg.Inject<IFoo>(), ctorArg.Inject<IBar>()));

What's actually the difference between using .ToConstructor and .ToMethod in an almost the same way:

Bind<IMyService>().ToMethod(
    x => new MyService(x.Kernel.Get<IFoo>(), x.Kernel.Get<IBar>()));

Is it just a syntax sugar to avoid using Kernel.Get<>() or is there something more that I'm missing?

Answer

Remo Gloor picture Remo Gloor · Jan 8, 2012

The first case behaves like To<MyService>() except that you explicitly select the constructor. This means the context is passed through MyService and you can use conditions for IFoo and IBar or one of their dpependencies where in the second case you get a new context for IFoo and IBar and you will not know that they are injected into MyService.

e.g.

Bind<IFoo>().To<FooA>().WhenInjectedInto<MyService>();
Bind<IFoo>().To<FooB>().WhenInjectedInto<MyOtherService>();

will not work in the second case.

Related questions

How do the major C# DI/IoC frameworks compare?

At the risk of stepping into holy war territory, What are the strengths and weaknesses of these popular DI/IoC frameworks, and could one easily be considered the best? ..: Ninject Unity Castle.Windsor Autofac StructureMap Are there any other DI/…

Read More
An object with the same key already exists in the ObjectStateManager. The ObjectStateManager cannot track multiple objects with the same key

Using EF5 with a generic Repository Pattern and ninject for dependency injenction and running into an issue when trying to update an entity to the database utilizing stored procs with my edmx. my update in DbContextRepository.cs is: public override …

Read More
Could not load file or assembly 'System.Web.Mvc, Version=3.0.0.0' or one of its dependencies

I am adding Ninject in MVC project using the following commands in Package Manager Console: Install-Package Ninject -version 3.0.1.10 Install-Package Ninject.Web.Common -version 3.0.0.7 Install-Package Ninject.MVC3 -Version 3.0.0.6 When I run the application, I get error like this: Could not load …

Read More