Question

How do I do change this piece of code to .NET 2.0 compatible by replacing the extension method to .NET 2.0 of equivalent?

public interface IMessagingService {
    void sendMessage(object msg);
}
public interface IServiceLocator {
    object GetService(Type serviceType);
}
public static class ServiceLocatorExtenstions {
    //.NET 3.5 or later extension method, .NET 2 or earlier doesn't like it
    public static T GetService<T>(this IServiceLocator loc) {
        return (T)loc.GetService(typeof(T));
    }
}
public class MessagingServiceX : IMessagingService {
    public void sendMessage(object msg) {
        // do something
    }
}
public class ServiceLocatorY : IServiceLocator {
    public object GetService(Type serviceType) {
        return null; // do something
    }
}
public class NotificationSystem {
    private IMessagingService svc;
    public NotificationSystem(IServiceLocator loc) {
        svc = loc.GetService<IMessagingService>();
    }
}
public class MainClass {
    public void DoWork() {
        var sly = new ServiceLocatorY();
        var ntf = new NotificationSystem(sly);
    }
}

Thank you very much.

Answer 1

Just remove this keyword from extension methods.

public static class ServiceLocatorExtensions
{    
    public static T GetService<T>(IServiceLocator loc) {
        return (T)loc.GetService(typeof(T));
    }
}

And call it as any other static method by passing instance of object which you are ‘extending’:

IServiceLocator loc = GetServiceLocator();
Foo foo = ServiceLocatorExtensions.GetService<Foo>(loc);

Actually this is what .Net 3.5 compiler does behind the scene. Btw suffix Extensions you can remove too. E.g. use Helper to not confuse people.