() => construct

Question

I am in the process of converting a project from visual studio 2005 to visual studio 2008 and came up on the above construct.

using Castle.Core.Resource;
using Castle.Windsor;
using Castle.Windsor.Configuration.Interpreters;
using CommonServiceLocator.WindsorAdapter;
using Microsoft.Practices.ServiceLocation;

namespace MyClass.Business
{
    public class Global : System.Web.HttpApplication
    {
        public override void Init()
        {
            IServiceLocator injector =
                new WindsorServiceLocator(
                    new WindsorContainer(
                        new XmlInterpreter(
                            new ConfigResource("oauth.net.components"))));

            //ServiceLocator.SetLocatorProvider(() => injector);

            // ServiceLocator.SetLocatorProvider(injector);
        }
    }
}

ServiceLocator.SetLocatorProvider(() => injector);

Can I get an understanding of what this is.

Answer 1

This is a lambda expression.

I guess that the SetLocatorProvider method has a signature like:

SetLocatorProvider( Func<IServiceLocator> callback ):

Now you have to provide such a callback. There are basically three options:

Use a method (always working):

private IServiceLocator GetServiceLocator() { /* return IServiceLocator */ }

ServiceLocator.SetLocatorProvider( GetServiceLocator() );

Use a delegate (requires C#2.0):

ServiceLocator.SetLocatorProvider( delegate
        {
            // return IServiceLocator
        } );

Use a lambda (requires C#3.0):
That's the code you see ...
Since there is no argument (Func<IServiceLocator> has only a return value) you specify this by using ():

ServiceLocator.SetLocatorProvider( () => { /* return IServiceLocator */ } );

this can be translated to

ServiceLocator.SetLocatorProvider( () => /* IServiceLocator */ );

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