An IoC-Agnostic Prism Bootstrapper

Prism from Microsoft Patterns & Practices leans on an Inversion of Control (IoC) container. While nominally indifferent to your choice of container, you have to work a bit to extricate yourself from its default choice which is Microsoft Unity. More so with some containers than others.

The sweat and tears flow in the “Bootstrapper” class with which you launch your application. Most Prism samples feature a Bootstrapper that inherits from “UnityBootstrapper”. “UnityBootstrapper” busies itself with registering and configuring a dozen or so Prism components in a manner characteristic of Unity and it unapologetically takes a hard dependence on Unity itself. You are welcome to write your own Bootstrapper base class from scratch; of course this entails reading and understanding what “UnityBootstrapper” does so you can reassure yourself that your replacement achieves the same effects. Who has time for that?

Almost a year ago I found myself writing a single application with three different client technologies, each dependent upon its own container. The three diverged in minor details – each was a different incarnation of a Container + ObjectBuilder – but the differences were sufficiently great that I felt compelled to unleash the Prism base bootstrapper class from its Unity chains.

Preoccupied with more important business, I took the most expeditious route. I salvaged as much of Prism’s UnityBootstrapper as I could while replacing its direct dependency on Unity library references.

Prism initialization is not something I want to own. When P&P updates its UnityBootstrapper, I want a quick, no-thought pathway to update my IoC-agnostic version.

The result was Cal.Bootstrapper (“CAL” is short for “Composite Application Library”, Prism’s official name) and some supporting types. Cal.Bootstrapper looks like a cleaned-up UnityBootstrapper. It goes through the same motions of registering types and configuring instances albeit with reference to a denuded IoC, shorn of all but the most minimal functionality. This, dear reader, will be my gift to you.

Recently, a few folks have wondered about replacing Unity with a completely different IoC container. The one I hear most often is StructureMap. Its author, Jeremy Miller, has several times entertained the notion of replacing “UnityBootstrapper” with something that reflects glory on StructureMap. Apparently he has better things to do. I guess I’ll tackle it.

The Goods

I’ve bundled everything described in this post into a 2 meg zip, PrismRI-Ioc.zip, downloadable from my company website. Do with it as you will.

Please note: I have no intention of maintaining this; don’t even ask.

No, This is Not the Right Way

My knowledge of StructureMap is deeply impoverished but, from the little I do know, I’m certain that the “proper” course is to abandon “UnityBootstrapper” altogether. But there’s a reason Jeremy hasn’t tackled this and no one seems to have done so for other IoC products either.

Nicholas Blumhardt, author of Autofac, took a crack at integrating Prism with his IoC back in August, 2009. He wanted to do it “the right way,” completely rethinking how a Prism app is bootstrapped and how application modules are written. He describes it here as a “work-in-progress”. I guess it took a little more work than he thought it would and he must have found something better to do because it doesn’t look like he finished.

I hoped to avoid this “road to good intentions” by doing it the “the easy way” which may be the “wrong way” but it works … which beats something that doesn’t.

I decided to change as little of the Unity-oriented Prism app approach as I could. I want to get something done. I want you to be able to convert your running Prism app with minimal effort.

Accordingly, my “Cal.Bootstrapper” mimics the “UnityBootstrapper” and it wallows in the style and ceremony that other IoC products despise.

Is it all that bad? Why am I changing my IoC container anyway? I ought to have a clear idea about what I want from an alternative to Unity. I’m wasting my time if I’m only replacing the UnityBootstrapper with something “better”. Frankly, I don’t care how Prism configures its minimal requirements. If I want StructureMap (or AutoFaq, Castle Windsor, Ninject, etc), it is because I prefer that IoC for registering and configuring my own application components. I may replace the Prism configuration eventually but right now that is neither my motivation nor my first step.

Therefore, although my Cal.Bootstrapper is ugly as sin, it will serve me for the nonce as I hope it serves you and I shall proceed to describe it without further apology. I will let it configure Prism the ugly way using my IoC container in place of Unity after which I am free in my own code to drive my IoC container as it was meant to be driven.

Battle Plan

A Prism application has a Bootstrapper class to configure the container, create and configure the main UI view called the “shell”, acquire application modules, and launch the application.

You are expected to write a custom Bootstrapper that inherits from a base Bootstrapper class provided by Prism (the aforementioned UnityBootstrapper). This base class handles the above inventory of start-up tasks. Your derived Bootstrapper is supposed to extend the base class by overriding certain abstract and virtual methods.

In other words, the bootstrapper is launch karaoke. You add your voice at predefined moments. It’s great if the music suits you. If you’re singing off key, you’re should stop faking it and write your own song.

Tempted as I was, I chose not to quarrel with this approach. In fact, I took a deep breath and then embraced it … for the reasons discussed above.

I decided to replace the UnityBoostrapper with an alternative base class (Cal.Bootstrapper) that does not know about Unity.

Your derived Bootstrapper will provide an IoC container to this base class, wrapped in a vendor-neutral “ContainerAdapter, and delivered to the base class by overriding its abstract “CreateContainerAdapter” method.

I have a few additional goals:

• “Improve” the UnityBootstrapper so I can figure out what it does.
• Make it easy to update my base class when (if) Microsoft updates the UnityBootstrapper.
• Minimize the effort to get my existing app bootstrapper deriving fro the IoC-agnostic base class.
• Minimize the changes necessary to convert my existing Unity-based Prism app.
• “Prove it” with an app Prism-aficionados know: the Prism Reference Implementation.

The original UnityBootstrapper is code only a mother could love. Long methods; much repetition; mysterious names. I can’t replace it until I understand what it does. My first step is to refactor it for readability. This is somewhat a matter of taste but I hope you’ll agree that the my revision, called “RefinedUnityBootstrapper”, is an improvement.

I mustn’t get carried away if I am to satisfy my second subsidiary goal. Too many improvements would hinder re-synchronization with Microsoft’s changes.

I want to prove that my approach works on an “application” that anyone can examine and that would be familiar to Prism developers. The Prism RI is the obvious candidate; that’s what I tackled.

I haven’t looked at the RI in a long time. The version on my disk dates from February 2009. That’s pre-Silverlight 3 and, although I had patched it for SL 3, it’s still old and funky. The UI doesn’t work the way it should: stock positions don’t change when you buy and sell, the “Watch List” feature is broken, the Silverlight version throws a recoverable exception when you sell more stock than you own.

But I didn’t have time to freshen it up, it was good enough for my purposes, and it’s all I’m going to give you.

Swappable Versions

This is a tutorial. I want you to be able to switch among different container implementations without changing the body of the application. I don’t have the time or the interest to do anything fancy.  In the “real” world, I’d make the change and discard the original.

The version of the RI you run depends entirely upon the executing version of Prism RI Bootstrapper class. The class is divided into two partial class files. One of them is constant. The other holds just the code that varies from container to container. The file with variations is called StockTraderRIBootstrapper.Ioc.Desktop or StockTraderRIBootstrapper.Ioc.Silverlight.

The variations are governed by compiler directives at the top. You uncomment ONE of them, recompile, and let ‘er rip. The example below shows the bootstrapper readied for StructureMap.

//***************************************************************************
// *** PICK YOUR BOOTSTRAPPER AND IOC CONTAINER WITH _ONE_ OF THESE DEFINES

//#define ORIGINAL_UNITYBOOTSTRAPPER
//#define REFINED_UNITYBOOTSTRAPPER
//#define UNITY_CONTAINER_ADAPTER
#define STRUCTUREMAP_CONTAINER_ADAPTER
//#define AUTOFAC_CONTAINER_ADAPTER

//***************************************************************************

Each variation takes only a few lines. I set the title text so you can see which version is running on screen (the original three letter “CFI” company name changes to one of “OUB”, “RUB”, “UCA”, “SMA”, or “ACA” to match your selection). For the Ioc-agnostic variations, there is an override of the method that creates the selected Ioc ContainerAdapter. The two versions pinned to the UnityBootstrapper (remember that I “refined” the UnityBootstrapper first simply to understand it better) have a shim method instead.

Incredibly stupid, I know. I’d never ship anything like this. I live with it because it’s a throw away demo and doesn’t merit the effort or complexity of proper decoupling. Or at least it doesn’t merit that attention yet.

The rest of the Prism RI stays constant. It took some work to keep it that way. Not a lot, fortunately; the Patterns and Practices people did a pretty good job of keeping the RI Ioc-neutral.

I won’t bore you with the details of my journey to this blissful place. They are chronicled in “PrismRIChanges.txt”, located in the PrismRI folder next to the Visual Studio Solution file, “StockTraderRI-IoC.sln”. The gist of it is

• Add the Ioc assemblies in a common directory structure
• Add the PrismBootstrapper solution with its Ioc-agnostic Cal.Bootstrapper and the Ioc-specific ContainerAdapters.
• Revise the start-up project, StockTraderRI, to access the above
• Replace references to “IUnityContainer” with “IContainerAdapter”
• Remove module references to Unity.

You’ll do pretty much the same if you convert your existing Prism application to another Ioc container.

ContainerAdapters

The fun is in the ContainerAdapters which implement the following interface:

namespace Cal.Bootstrapper {
  public interface IContainerAdapter {

    IContainerAdapter RegisterInstance<T>(T instance);

    IContainerAdapter RegisterType<TFrom, TTo>(
        ContainerRegistrationScope scope) where TTo : TFrom;

    IContainerAdapter RegisterType(
        Type fromType, Type toType, ContainerRegistrationScope scope);

    IContainerAdapter RegisterTypeIfMissing<TFrom, TTo>(
        ContainerRegistrationScope scope) where TTo : TFrom;

    IContainerAdapter RegisterTypeIfMissing(
        Type fromType, Type toType, ContainerRegistrationScope scope);

    T Resolve<T>() where T : class;

    object Resolve(Type type);

    T TryResolve<T>() where T : class ;

    object TryResolve(Type type);
  }

  public enum ContainerRegistrationScope {
    Singleton,
    Instance,
  }
}

Not so bad if you know your container. Clearly IContainerAdapter must be so dumb that any IoC Container vendor can support it. It needs to be just smart enough for the base Bootstrapper class to configure Prism. Fortunately, this challenge is easily met.

The code tends to be boilerplate. Autofac took a little more work (see below) but still weighs in at only 180 lines.

You also have to write an adaptor that implements Microsoft.Practices.ServiceLocation.IServiceLocator; virtually everyone has done this already.

IoC Containers Demo’d

I’ve tried this approach with three IoC Containers: Unity (Unity v.1.2.0.0, ObjectBuilder2 v.2.2.2.0), StructureMap (v.2.5.4.0), and Autofac (Desktop: v.1.4.5.676, Silverlight: 1.4.4.572).

You should know that I am not an expert in any of these containers. In fact, I just winged it, especially with StructureMap and Autofaq about which I know squat. I figured I could download them, skim whatever documentation they offered, and get something to work adequately for Shmoes like me.

It’s not quite that easy and I have low confidence in my use of these containers. Their authors are invited to lend a hand improving matters … after they’re done laughing.

I wanted to show at least one non-Unity container for both desktop and Silverlight applications. StructureMap doesn’t have a Silverlight version yet (come on, Jeremy). I tried Autofac because it does have a Silverlight version.

I’m glad I did. The StructureMap implementation was a breeze. Autofac was much harder. I’m not trashing Autofac. It just happened to be harder for me, partly due to my ignorance and mostly because of the position Autofac takes on resolving unregistered types.

Major Container “Gotcha”

Container differences matter! One pervasive Prism practice in particular relies on a Unity default behavior that other containers do not observe. It’s serious enough to influence your choice of containers or make your conversion substantially more difficult.

Prism instantiates a lot of its own components with unregistered public concrete classes. For example, somewhere in the bowels of RegionManager initialization, it resolves “DelayedRegionCreationBehavior”. This class is never registered with the container.

Unity is ok with this. When asked to resolve an unregistered public concrete type, it treats the type as if it had been registered and scoped as an instance (i.e., you get a fresh instance each time). Both TryResolve and Resolve behave this same way.

Prism components count on this default Unity container behavior. What if you change containers?

StructureMap has the same default behavior when resolving an unregistered public concrete type. However, it’s TryResolve equivalent, “TryGetInstance”, return null. As I write, I have not detected a consequence of this difference; but I know it’s waiting in the grass somewhere.

You could argue all day about whether a container should return null or return an instance the way Unity does. You could argue whether it should default to Singleton or Instance scope.

Autofac punts. If you attempt to Resolve an unregistered type, it throws an Autofac.ComponentNotRegisteredException with a clear message. “TryResolve” returns null, which is the sensible thing to do.

Aside: the three ContainerAdapter files in my sample implement a “ContainerPlay” class that reveals these differences.

I can’t quarrel with Autofac’s choice but I sure paid the price for purity. I had to hunt down all resolutions of concrete types and manually register them during AutofacContainerAdapter initialization. Unfortunately even that is insufficient. Many class constructors take parameters defined by concrete types. The container will attempt to resolve these and will throw at runtime. There aren’t integration tests to detect these automatically so I have to wander through the app under the debugger. I still haven’t got it to work.

It was easier to get the Prism RI working with StructureMap. I have assumed that the only critical difference is with explicit “TryResolve” calls. I haven’t encountered any optional constructor parameters so I expect StructureMap and Unity to resolve these in the same way.

I searched the Prism and RI source code for “TryResolve” calls involving concrete type. There weren’t many of them. I only found one of potential consequence. The base bootstrapper calls “TryResolve<RegionAdapterMappings>”. Fortunately, it also registers RegionAdapterMappings explicitly so resolution is always successful. Perhaps I was luck. Remember to be careful how you use TryResolve in your application.

The net of it is that containers differ. Prism should not have relied on a Unity-specific type resolution feature. If you have done so in your Unity-based application (as I have), you too are vulnerable.

Where Did The Tests Go?

I removed the test projects from the Prism RI and the Composite Application Library projects that go with it. Why did I do that? laziness?

I really thought this simple task would take maybe a long day at most. Stripping the tests away from the start was supposed to help me stay in the time box. It was going to be non-trivial to setup Prism’s test environment, convert the tests, and repackage for distribution to you. I didn’t think I could afford it.

The point of the exercise was to demonstrate how to liberate your application to use an alternative container. I wasn’t trying to deliver a product and there is limited value in tests for a version of the Prism RI that is (a) obsolete and (b) irrelevant to your application.

Unfortunately, this “simple” task kept expanding in scope; it took four long days. Geez like that never happens.

Now that I’m “done” I wish I had those tests back, the UnityBootstrapperFixture in particular. Debugger testing is painful as we all know. Had I committed to automated tests, I would have written something better than the idiotic compiler-directive-based approach to swapping containers. Sure it would have cost me something – a day? – to get it right, a day I didn’t want to spend. But if someone wants to take this further, the tests would accelerate his progress greatly and imbued his efforts with confidence. Mea culpa.

I wonder if some kind soul will restore them?

Happy New Year, everyone!

PDC 2009 Session Links

I extracted the session titles and links into this PDF to make it easier for me (and for you) to find and navigate to the PDC 2009 session materials. Hope it works for you.

Easing into Prism

I received a familiar email today:

Is it possible to start slowly with this Prism stuff and work my way into it gradually. Can I get something running quickly with DevForce as I know it now? My client has seen a prototype and I need to construct it soon. Then can I come back later and modularize the whole thing behind the scenes?

Here’s my reply:

You do not need Prism to get started!  You can introduce it into your application as you see opportunities that make sense to you. Prism is not a monolithic framework. It is a small collection of free-standing components that also work well together. You can adopt it a piece at a time; some of it you may comfortably ignore.

It’s definitely worth reading about. It’s worth looking at the Reference Implementation and the Quick Starts. Get the Composite Application Guidance book from Patterns and Practices, look at what folks are doing with it and saying about it.

Don’t get hung up on Prism itself. It is guidance first and implementation second. Poke around. See how other people tackle some of the same concerns. You might look at Caliburn, for example.

In other words, take your time and educate yourself.  You don’t have to dive into the deep end.

However, I feel strongly that you should start wrapping your head around Dependency Injection (DI) and Inversion of Control (IoC) containers as soon as you can.  They will completely transform the way you write your application. They will position you for future modularity and make your code ever so much easier to maintain.

Learning IoC is also a great career move.

When you see yourself writing “new XXX(…)” you will learn to stop and ask yourself, “Do I really want to lock myself into the XXX type or would I be better off if XXX were delivered to me instead?”  In recent years my answer has increasingly been to avoid “new” and let the IoC construct and inject the instance I need.

Don’t get carried away now. It’s a shiny new toy. Take it easy. But get used to it.

I know you asked about Prism and here I am waxing on about IoC. I only go on about this because your decision to use or not use DI/IoC is fundamental. Prism (and its ilk) will come along naturally if you use DI; they won’t seem so natural if your application is not DI-ready.

I promise the effort of learning DI (and it does takes some effort) will pay off quickly … and for the rest of your career. The principles are fundamental to emerging Microsoft technologies (see the Managed Extensibility Framework – MEF). Dependency Injection is the primary vehicle for implementation of most modern application development patterns.

You have plenty of IoC containers to consider. Microsoft Unity is one choice but by no means the only one: AutoFaq, Castle Windsor, Ninject, and StructureMap are popular (apologies to any I omitted).

Do not be overwhelmed! These alternatives are vying for your affections with tons of features and you may easily become convinced that DI is super-complicated.

You can ease into DI. Take a look at our “Prism Explorer” (which uses Unity); you’ll hardly notice IoC but it’s there. I limited myself to the simplest Unity techniques. If I remember correctly, I only use constructor injection, I register very few interface types, and I don’t use any of the attribute markup. You can go amazingly far without any advanced IoC features.

In sum, get going on your application and do not let these technologies distract you. They are important and valuable but you don’t want to destroy your business relationship by drowning in technologies that you know nothing about.

Get acquainted with Dependency Injection first and start using it experimentally. Learn about Prism in all that spare time.

Try partnering with someone who has been down this road before. If that is not possible, find a local users group and latch on to other like-minded developers. It’s much more fun when you play with others.

Young @ Heart: The (2007) Movie

Stumbled into “Young @ Heart”, a documentary about a New England choral group performing punk, rock, and R&B covers; the hook is that the members are well over 70 (high of 92).

Sounds like an opportunity for terminal cuteness … “oh those feisty seniors … isn’t it amazing that they can sort of sing at all at their age? … it’s so inspiring!”.  That’s exactly the sense you get from the trailer which is delivered with the typical phone-it-in Fox Searchlight style. Exactly the kind of movie I avoid.

But this one caught me completely by surprise and I’m still roiling with emotions a day later. I’m trying to figure out why.

It should have been utter treacle like one of those sentimental movies about animals, or kids, or illness, or the mentally infirm. Instead it’s a rich character study in which each member of the cast takes you somewhere you’re likely to go … somewhere you want to go … if you’re lucky enough to live that well.

Singing is the glue and reason enough to watch. The songs - well-known pop tunes of youthful love, rage, despair, and hope – confess new moods and meanings as sung by performers far from adolescence.  The juxtapositions can be simple fun as in the raucous “I Want to be Sedated”, given literal treatment by a cast for whom the wheelchair is a serious threat. Or it can rip you open as when Bob Knittle’s rich baritone pleads “I will try to fix you” to the barely perceptible beat of his oxygen machine, counting down toward the inevitable. It would be contrived if it didn’t actually happen, inadvertently, before a packed house of loving fans.

The heart of the movie is the interviews and the lives of the cast as they orbit the rehearsal hall. The authenticity is striking. At a jail house concert the camera lingers on the prisoners’ faces each surrendering a thought of present loss or worrisome future. They are not being entertained (although they think they are); they are transported to the company of someone they miss, of someone they may become.

Death is a looming presence. Close as he is, the cast are no more ready for him than we are.

It’s not great filmmaking. It’s great human material triumphing over the pedestrian. It’s people being themselves, striving for meaning and community, just a few feet ahead of us down the road we travel together.

Patterns and Frameworks

I just returned from the Microsoft Patterns and Practices Summit 2009 which may be my favorite Microsoft conference. Great for exposure to customers with real applications and to the wonderful, dedicated Microsoft developers who aspire to serve them. More on this in another post. I have another point to make here, which is …

Patterns are not Frameworks. We should draw a bright line between Patterns and their Implementations. A pattern only becomes a pattern if and when there are multiple implementations. You don't know a pattern well until you've seen more than one implementation. If there is a single, canonical implementation, the thing is not a pattern, it’s a framework.

“Duh” you say. We know this. And yet it eludes us in practice.

I had numerous conversations about this with folks who work in PnP. The conversation goes something like this:

The Conversation

“We are not a product group. We don’t want to be a product group.

“We’re trying to provide guidance to consumers of Microsoft development products. We are reluctant even to say ‘best practices’ anymore. It’s just the best guidance we can give today, built with time, and commitment, and our access to experts inside and outside Microsoft.

“We’re answering the customer call for Microsoft to demonstrate how to use its own products in real applications.

“This bleeds inevitably into more general questions about how to build applications and soon (and properly) we investigate and describe general design and implementation patterns that go beyond the particulars of Microsoft products.

“It’s not enough to talk about the patterns. We need to demonstrate those patterns … express them in real code that works with Microsoft technology.

“That is when it starts to get away from us. Our guidance, as it becomes code, starts to cover more and more customer cases. It begins to harden and the pattern becomes harder to see behind the bells and whistles. Customers say ‘wow, can I use that in my application?’ and we say ‘sure’. They say ‘it would really help our particular situation if it also did this’ and we say ‘sure’ again.

“Then they want us to give it a name, package it up, support it, develop a roadmap. They want us to productize it … and we start to do that because serving customers is also our mission. And, in our (not so) secret hearts, we all want to ship products … we’re wired that way.

“Then we start worrying about backward compatibility … because customers get angry at us if we change anything

“Then others in the community, especially the Open Source community, get on our case for having sucked the oxygen away from alternative implementations that may be better in many scenarios. They say we have imposed, de facto, a particular implementation of the pattern; people can’t tell the difference between the pattern and what Microsoft did to it. And I see their point.

“And now we have old code (e.g., CAB) that no longer represents our current thinking … that, in fact, embodies practices we would counsel against today … and we cannot walk away from it.

--

I don’t know that there is an easy answer to this one. I’m not willing to place all the blame on PnP either. The customer should know better.

“Best Practices” do not sit still. They evolve, leaving behind a trail of “formerly best practices” to which millions of dollars and entire careers are firmly attached. PnP is pulled in one direction by its responsibility to offer the best current guidance … and by its responsibility to customers who have placed big bets on its past guidance.

Perhaps we need some different rules of engagement.

Explicit Shelf Life

What if PnP put a “Sell By” date on their code? What if it had a shelf life and warning label: “Use with caution. Do not expect support beyond 3 years”. Stamp this at the top of every piece of code and every web page.

Then mean it. If you need to break, you break. Customers need to know that you are serious about your commitment to giving them the best advice you can and you do them no favors by clinging to outdated code.

This happens in OSS all of the time. Dead bodies are strewn everywhere.

You can do this. Microsoft can’t but you can. I think you can wean your customers away from thinking of you as a product group. If that means fewer customers served … that may be for the best … for everyone: your customers, you, and Microsoft itself.

Play Well With Others

My thesis again: a pattern is independent of any one implementation. You don't know a pattern well until you've seen at least two implementations.

What if PnP routinely called out the other implementations of the patterns they describe? Front and center, not as an afterthought. Openly encourage customers to look at these alternatives … if only to gain a contrasting perspective on the PnP guidance.

One of the best ways to learn about the Composite Application Block (CAB), for example, was Jeremy Miller’s “Build your own CAB” series. I assure you I had no intention of following Jeremy’s advice and building my own CAB. It didn’t even occur to me. But that series was the best (unintentional) documentation of CAB I ever found, It introduced me to different ways of thinking about each issue (e.g., Event Aggregation and Dependency Injection). I learned indirectly what CAB was doing and the consequences of my choice. I’m not saying the consequences were all bad either; but there were consequences and I only recognized them in the oblique light cast by Jeremy’s series.

PnP might do more to highlight these alternatives and to encourage discussion about the contrasting choices. People who come to Prism should learn … right there on the home page … that a Caliburn exists. When they come to the Unity home page, they could learn that there are 5 to 10 other popular IoC containers to choose from and find links to learning more about IoC practices.

[I was just on the Unity page. It’s a fine product home page; it is not fine for guidance about Dependency Injection and IoC in general.]

I don’t think that PnP should endorse Caliburn or anything else for that matter. I’m not suggesting that PnP’s output is inferior or that PnP should express less than abundant enthusiasm for its own work.

I am saying that PnP is presenting itself as a product purveyor in a manner that conflicts with its role as a trusted source of guidance. This ensures that it will be trapped into long term support commitments, the kinds of commitments that some people there tell me they do not want.

PnP could say in some unambiguous fashion, “my dear customer, we offer a wonderful implementation of this pattern. HOWEVER … you ought to look at some alternatives, not only when first choosing your approach but also throughout your application development; there’s gold in seeing how others approach these same problems.”

True Open Source

What if PnP could accept contributions from the field? I don’t mean through “Contrib”; I mean directly into the guidance itself.

What if PnP developers actually read some of the Open Source code out there?

I’m pretty sure the legal guardians won’t permit it … in which case “Contrib” is the best they can do.

Conclusion

They call it "Microsoft Patterns and Practices", not "Microsoft Tool and Die".

It is time for customers to pull back from unrealistic expectations of Patterns and Practices. They are not your application infrastructure outsourcer. They are a trusted source of guidance. Rejoice if they provide more but do not expect or demand it.

Patterns and Practice doesn’t need to change what they build. I do think PnP can rethink its commitments to prior output. It can do a much better job of promoting the spirit of exploration and directing its community to external resources that offer contrasting implementations and points of view.

And now I descend from this soap box … in search of another.

Man and Superman

I was reading Jeremy Miller’s musings on “Two Types of Developers”.

Developers fall into two different extremes … Some developers can jump right into any technology and find out how best to use it and new ways to twist it and apply it without really questioning the “goodness” of that technology.  Others look at a technology with preconceived notions of how it should work and are quick to drop a technology when it doesn’t fit their vision of “good.”

I am reminded that there are two kinds of people in this world: the people who divide the world into two kinds of people and the people who don’t. I am one of those two kinds of people.

What Jeremy really means it that there are two developer mindsets. Actually-existing developers indulge both modalities as he also observes in this second paragraph. Still, the thrust of his argument is that developers habituate to one or the other extreme.

Jeremy aligns himself mostly with the second. He describes an encounter with someone who, as Jeremy would have it, is inclined to the first.

I happen to have read the blog post on exhibit, know both parties (call the other “B”), and participated in some of the exchange that ensued. It got me wondering whether I buy Jeremy’s dichotomy.

Jeremy strives to be non-judgmental, averring potential advantages on both sides. I suggest that his phrase “without really questioning the ‘goodness’ of that technology” gives the game away.

I know “B” and he is a curious fellow (double entendre intended). His curiosity is evident in the post and manifold in conversation. “B” never takes a technology on face value, certainly not “Prism” which was the technology at issue in this example.

It may be relevant to note that “B” was deeply involved in Prism development. He is obviously comfortable with it. But “B” was as deeply involved in the debates, disappointments, and compromises that are inevitable when one works collaboratively on a framework. He may be blind to some of its faults but he can’t be accused of being uncritical by nature.

What happened here is that “B” chose to implement a solution to a problem using technology that Jeremy dislikes. One may say so. One may ponder the reasons. But to leap to the conclusion that “B” (or anyone who chooses similarly) is simply “unquestioning” …  that is unjust.

Worse, it is lazy.

It forecloses a genuine attempt to investigate how developers actually make choices in the real world of customers and deadlines.

Are there drudge journeyman programmers who paint by numbers? Sure … but they aren’t relevant to this discussion and that is not what Jeremy thinks of “B”.

Do we often cheerily follow the easy, well-trod path? Of course. Do we challenge our every decision to be the best possible in the abstract. No. None of us do. Could “B” have made a better choice than Prism… even in his particular circumstances? Maybe … which makes it worth pursuing with “B” .

But Jeremy’s point isn’t that we are prone to be the willing captives of our familiar tools. No, he claims we are by nature either slaves or freeman, the “last man” or the “Übermensch”. That is the true import of his “interesting taxonomy of developers that I’ve observed for years”.

The earth has become small, and on it hops the last man, who makes everything small. … One still works, for work is a form of entertainment. But one is careful lest the entertainment be too harrowing. One no longer becomes poor or rich: both require too much exertion. … 'We have invented happiness,' say the last men, and they blink.

Behold, I teach you the overman. The overman is the meaning of the earth.Let your will say: the overman shall be the meaning of the earth! I beseech you, my brothers, remain faithful to the earth, and do not believe those who speak to you of otherworldly hopes!"

- Nietzsche's Thus spoke Zarathustra

It’s thrilling to hear … but I am not buying it.

I’m a huge Jeremy Miller fan; this was not his best day.

Silverlight Spy 3 – First Look

Silverlight Spy 3 was just released. I think you’ll want this in your tool bag right away. Why? Because it is a great way of seeing what’s going on in your Silverlight application … and twiddling its appearance … at runtime.

It is especially helpful if you’re building a compositional application of many, independently-designed views; you want to see them playing together and understand what’s happening.

Quick Tour

I’m looking at my Prism Explorer demonstration app right now. This demo shows our DevForce Silverlight Data Services product working with Prism.

Fired it up in Visual Studio (to get the Cassini server side going), then pasted the URL (http: //localhost:9006/) into Spy’s address bar. Spy fires up the client in its browser just fine.

Spy drew the red highlight box, not me. I held down the ctrl + shift keys and moved my mouse around the browsed page; as I did, Spy highlighted each element in this manner; and then I clicked on the address to set the focus as you see it.

Now I swing over to the Explorer view and I see that the address is a TextBlock in the middle of a DataGridCell … deep in the visual (or logical) tree that begins with my Prism shell. I love being able to start from something I see on the page right to the element in the object tree.

I get the same effect in the other direction by navigating from the tree: select a node and watch Spy highlight the corresponding visual real estate in its browser.

I can see the XAML for this TextBlock in Spy’s View window:

Suppose I want to see what would happen if I gave the address a little more air. I open Spy’s Properties window, locate the Padding property and try “20” all around. I see the effect immediately:

Peeking and tweaking the look on the fly is value that can hardly be overstated especially in a composite app. Sometimes you just have to see the app run in a production context with real data behind it to understand what is going on. Adjusting some values to visualize how it might look after correction … that’s worth something to me.

Spy integrates seamlessly with Reflector so I can poke around in the client-side source code while in Spy. First, I tell Spy where to find Reflector through Tools / Options / Reflector. Then, in the Explorer window, “Object Browser” node, I navigate the assemblies in the XAP:

The View window exposes the disassembled code using Reflector:

I can also spy on other people’s applications. Now, when I see an effect I like, I’ll have a fighting chance to figure out how it’s done. Nothing evil in that.

Perhaps more productively, Spy can help me better support my customers. I don’t have their code. I don’t want their code! Now I can fire up their app in Spy from out here in Stinson Beach (yes, kicking back with the blog) and gain immediate insight. Having reflector baked in makes it easy to walk their code too.

Helpful Touches

Spy let’s me monitor mouse and key events which I can filter. In this snapshot, clicking on the event also takes me to the associated visual element.

I like to know when my app is visiting the server. Fiddler, Firebug (FireFox), and Web Development Helper (IE) are superior tools for the in-depth analysis. But if I just need to know that something went over the wire and peek at the headers, Spy does nicely. In this snap I just asked for a projection over all customers and their orders:

The top window is a grid of the traffic; double clicking a row reveals the headers panels in the lower half.

There’s a Performance Monitor with the visual familiarity of the one in Windows Task Manager.

The processor metric seems parallel to the Task Manager’s. The memory metric probably tracks just your app’s usage although how and how precisely I can’t tell. I noticed unpredictable figures simply by refreshing the application address to restart the app. I think of it as a rough gauge of relative behavior. You’ll get a general feel and you might be able to detect some memory leaks this way.

There are other goodies. These are just the features that attracted my immediate attention and made me want to buy.

Price

Spy was free in earlier incarnations. It now sells for roughly US$100 for a personal copy. You can download an evaluation copy that’s good for 27 days.

Frankly, I’m glad to see a price. I love “free” as much as the next guy but nothing is truly free. I want Spy’s author to keep improving this tool and he has to make a living at it to do it well. I’m bummed when a great free tool comes along and then it just sits there, waiting upon the author’s free time to answer questions, fix bugs, and take the next giant leap.

The biggest shortfall (as I will repeat) is the utter absence of documentation. With a little dough, Koen Zwikstra - the man behind spy - can afford to hire a tech writer and cut some videos.

Full disclosure: I got a free copy as an MVP. This review, however, is entirely my idea with no promise of reward.

Wrap Up

Silverlight Spy 3 is a super tool and a fine piece of work. Runs like a top. No install issues, no runtime glitches so far.

No documentation! None that I could find. This is a huge weakness. Thank goodness for Koen’s Channel 9 video with Adam Kinney recorded at MIX in March 2009; it opened my eyes to the potential and gave me valuable operating clues. How else would I discover “Ctrl+Shift+Mouse+Click”? Web search revealed nothing else (there is material on Spy 2).

Fortunately, it is pretty intuitive. Just bang around on it awhile and it starts to make sense. But some kind of guide needs to come out soon.

I’m hopeful this introduction piques your interest and gets you started.

A few minutes with Spy and you remember in a hurry never to put anything secret in your Silverlight client; that’s the wrong place for the Coca Cola recipe. Sure other tools can do it …. but Spy makes it so easy.

Go Spy!