Ninject - How to dynamically select an implementation to bind to an interface

问题

I'm currently using Ninject to create instances of interfaces in a WCF Services application.

Bind<IObjA>().To<ObjA>().InRequestScope();
Bind<IObjB>().To<ObjB>().InRequestScope();
Bind<IObjC>().To<ObjC>().InRequestScope();

It works great, but we are going to have several implementations of IObjC. What options do I have for continuing fluid assignment of implementation to interface for IObjA/IObjB but allowing for configurable assignment for IObjC?

I found a related question on SO but I don't know if I can support both a fluid and a configurable approach simultaneously.

For example, can I use Ninject.extensions.xml for IObjC while continuing to use the above approach for IObjA and IObjB?

Is it advisable to have conditional assignment for IObjC? That seems dirty but at the same time appears very simple.

if (condition1)
  Bind<IObjC>().To<ObjC1>().InRequestScope();
else if (condition 2)
  Bind<IObjC>().To<ObjC2>().InRequestScope();

Also, I know other frameworks like Castle support XML configuration but I would like to continue using Ninject.

回答1:

1 - your bindings to IObjC have nothing to do with any other bindings. it doesn't matter where, when, or how you bind other services.

2 - you can use the XML extensions, but I would ask why you think you need it to be configurable.

3 - there are 2 possibilities for your conditional. first is that you want to make a decision at startup to determine whether to use ObjC1 for the entire lifetime of the app, or ObjC2. if that's the case, your code is ok. however, if you want to dynamically decided which object to use each time you resolve the binding, you will need to put the condition inside your binding, like so:

Bind<IObjC>().ToMethod( ctx => condition ? ctx.Kernel.Get<ObjC1>() : ctx.Kernel.Get<ObjC2>() );

alternately, you can use Named bindings:

Bind<ILog>().ToConstant( LogManager.GetLogger( "Accounting" ) ).Named( "Accounting" );

or "When" conditions to help:

Bind<ILog>().ToConstant( LogManager.GetLogger( "Background" ) ).When( context => context.Target != null && context.Target.Name == "backgroundLogger" );

来源：https://stackoverflow.com/questions/4606848/ninject-how-to-dynamically-select-an-implementation-to-bind-to-an-interface

标签

ninject