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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.

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Mayo
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1 Answers1

5

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" );
Dave Thieben
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    2- Imagine that you want same programm (.exe) at different machines, reading data from different databases or XML (not the same data structure) so you need to configure wich DAL to use in each case. How would you do that? – Morvader Nov 06 '12 at 12:43
  • would you not just have different connection strings in the app.configs? otherwise, that would be a good time to have a XML configuration. – Dave Thieben Nov 06 '12 at 18:29