I’ve been working with the 3.5 Framework pretty much exclusively for last 3 months and I just recently ran across one of the new features that I some how missed, Dictionary & Collection Initializers.

Before the C# 3.0 the only collections you could initialize in-line where arrays.  This always left me doing things like:

List<string> list = new List<string>(new string[] { "Cubs", "Sox" });

Now, you can use the same syntax to declare non-array collections as well as dictionarys. Declaring the same collection now looks like this:

List<string> list = new List<string>() { "Cubs", "Sox" };

Collection initializers are great and all, but using this on dictionarys is really cool especially when I am prototyping abstract service factories and I don’t want to have to declare a static method to initialize the dictionary.  I wrote this piece of code today and was amazed at how clean it looked:

public static class ServiceFactory

{

    private static Dictionary<Type, Type> ServiceDictionary = new Dictionary<Type, Type>()

    {

        {typeof(IValidateAddress), typeof(USPS.AddressValidationService)},

        {typeof(ICityStateLookup), typeof(USPS.CityStateLookupService)}

    };

    public static TService CreateService<TService>()

        where TService : IService

    {

        TService service = (TService)Activator.CreateInstance(ServiceDictionary[typeof(TService)]);

        service.Initialize();

        return service;

    }

}

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