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Refactoring to Patterns: WPF Edition Part 1 The Vision

I need to come up with a shorter title. Yesterday A few days ago, I gave some background on “Flow”, I know you guys are itching to get into some code; but remember we’re also attempting to talk about engineering software. Code is just one part of the engineering process.

I know there has been a lot of disdain lately for "”Big Process” or over documentation. But there are some documents that are worthwhile whatever methodology your subscribe to. One of those documents is the project vision and scope. Essentially, your project vision provides guidance for what the goals of the system are. As a rule of thumb, when considering a requirement ask “does this align with the project vision?”

I don’t believe much in process for process’ sake. I think Jeff Atwood said it best (in a post that I read as a result of my experiment), there is no recipe for the perfect program. Patterns, practices, and principles are not prescriptive, blindly following them is akin to trusting Google maps to get you to a destination in a strange town during construction season. In many cases, you’ll be just fine, but there will be those times when you wish you were more familiar with Milwaukee the town you’re driving through.

That being said, I feel that creating a project vision is an essential first step in starting a software project. The process (like making a business plan) makes you think, “Why am I doing this?” In many cases, a well-written vision will help you sell a project to management. In other cases, the vision serves as little more than than a daily reminder of what you’re trying to do. From a project management perspective the scope portion of the vision helps the PM decide if a feature is in or out for a project. Of course it can be adapted to fit whatever process you’re using. So if you’re doing agile or iterative development, you’d have a broad project vision and scope as well as a more narrowly focused iteration scope that says what’s in for a given iteration.

Up until now, my vision has been somewhat amorphous. The summary on the project page for “Flow” on codeplex is the closest I have to a project vision. Let’s rectify that situation.

First Draft

“Flow will be the most awesome software ever created. It will be able to read the user’s mind, anticipating what they want to do and respond accordingly. Flow will be so perfect that people will be willing to spend their life savings to acquire it.”

Although it would be great for “Flow” to possess these qualities, this doesn’t work very well as a product vision. Before we dissect it, we need to know what qualities make a product vision good. Fortunately, there is a lot of material available for someone learning about project management. Of course, one of my favorite starting points over the past few years has been Wikipedia. After a few steps of searching (which would be shareable within a completed version of “Flow”), I found the SMART acronym. Basically the product vision should be:

  • Specific: state the vision in clear terms, making a precise definition of what’s expected from the final product
  • Measurable: in other words it should be quantitative rather than qualitative.
  • Achievable: you can set all the goals you want, but if their outside the realms of reality, they’re pretty useless
  • Relevant: if you’re making a toaster, your customer won’t really care if it can be used to steam press their clothes (unless you’re selling one of those Swiss Army appliances you know what I mean)
  • Timely: if you don’t put limits on delivery of your product, you’re likely to be lapped by the competition

I hope you can see why my original vision isn’t very SMART. Usually faulty goals within a vision aren’t that obvious. They’re more insidious like “…the best toaster on the market”. (Coincidentally, if you’re asked that question on an interview, they want you to question the definition of the best, not go about proving that it is.)

Once More With Feeling

Anyway, let’s try again to envision “Flow”.

“Flow” will be a desktop portal that provides a single point of entry to a users’ information while synchronizing it between their devices. Here are the desired traits of Flow:

  • Extensible:  Flow will expose a plug-in architecture that enables extension of the application to include data from other information sources as well as different methods of visualizing that data.
  • Social: Flow will allow users to share their data with their friends, family, co-workers, and the general public.
  • Personal: Flow will allow users to take control of their information, enabling them to annotate, link, and tag it.
  • Contextual: Everything we do with our computers has a context, Flow will help users preserve that context so that when they are distracted or need to switch contexts they can easily return to what they were doing.
  • Discoverable: Flow will help users discover new features of the application and/or plug-ins for the application that will help them get more done. Think last.fm or Amazon recommends except for plug-ins.
  • Accessible: Flow will provide a framework that makes it easier for information to be organized and presented for the impaired.

There we are, I think our vision meets the SMART guidelines, with the exception of Timely. We haven’t placed a time frame on the release of Flow. It’s somewhat difficult for me to time this. I have a day job and family. (Including a new child on the way.) My heart wants to have the first version available by June. Reality says it will most likely be a Beta in September and V1 at year’s end.

Of course all of that could change should more people volunteer to help (it is an open source project after all). Even then, there is a limit to how effectively the work can be distributed. We’ll see what happens though.

Static Reflection: Say What?

There’s a new oxymoron going around call Static Reflection. The basic gist is that by using expression trees you can do things that appear to be dynamic but in reality are checked at compile time. Like for instance, getting the name of a property for firing an INotifyPropertyChanged.PropertyChanged event. My colleague, Jon Fuller, showed me his code for Method Guards and my first comment was that this would be a great tool for implementing INotifyPropertyChanged. He informed me that he already went there and showed me that code as well.

I wasn’t too happy with the idea of wasting your sole base class on NotifyPropertyChanged so I suggested that we use extension methods instead. After a bit of finagling with the framework (Events don’t like to be fired from outside their declaring class), here is the result:

        public static void SetProperty<T>(this INotifyPropertyChanged source, 
						Expression<Func<T>> propExpr, 
						Expression<Func<T>> fieldExpr, 
						T value)
        {
            source.SetProperty(propExpr, fieldExpr, value, () => { });
        }

        public static void SetProperty<T>(this INotifyPropertyChanged source, 
						Expression<Func<T>> propExpr, 
						Expression<Func<T>> fieldExpr, 
						T value, 
						Action doIfChanged)
        {
            var prop = (PropertyInfo)((MemberExpression)propExpr.Body).Member;
            var field = (FieldInfo)((MemberExpression)fieldExpr.Body).Member;
            var currVal = (T)prop.GetValue(source, null);
            if (currVal==null && value==null)
                return;
            if (currVal==null || !currVal.Equals(value))
            {
                field.SetValue(source, value);
                var eventDelegate =
			(MulticastDelegate) source.GetType().GetField(
				"PropertyChanged",
				BindingFlags.Instance | BindingFlags.NonPublic).
				GetValue(source);
                Delegate[] delegates = eventDelegate.GetInvocationList();
                var args = new PropertyChangedEventArgs(prop.Name);
                foreach (Delegate dlg in delegates)
                {
                    dlg.Method.Invoke(dlg.Target, new object[] { source, args });
                }
                doIfChanged();
            }
        }

Now you can use a strongly typed NotifyPropertyChanged declaration without using your base class

    public class PersonStaticReflection : INotifyPropertyChanged
    {
        private string _firstName;
        private string _lastName;
        public string FirstName
        {
            get { return _firstName; }
            set { this.SetProperty(() => FirstName, () => _firstName, value); }
        }
        public string LastName
        {
            get { return _lastName; }
            set
            {
                this.SetProperty(() => LastName,
                                 () => _lastName,
                                 value,
                                 () =>
                                     {
                                         // do something useful here
                                     });
            }
        }

        public event PropertyChangedEventHandler PropertyChanged;
    }

For those concerned, you can statically cache the PropertyChanged field in a dictionary mapped to the object type so that you only have to reflect on it one time.

Refactoring to Patterns: WPF Edition Part Zero

I guess I should give you some background before I go much further. The application we’re discussing here is called “Flow”. The name is metaphoric in several ways. The first metaphor is Flow as in a flow of thoughts or stream of consciousness. The second reference is to the work of Mihály Csíkszentmihályi, who has written a lot of books about the concept of “Flow” – a state of total immersion in one’s activities.

Stream of Consciousness

My first impetus in designing “Flow” was dissatisfaction with my browsing experience. I wanted an application that would capture my stream of consciousness as I browsed the web – creating a mind map if you will. For an example of what I mean, read one of Jeff Atwood’s posts and open a new tab for every link in the post (to keep it fair only use the self-referencing links you can also skip any links that you know are dupes). Then do the same for each tab you’ve opened. Once you’ve done that you’ve got a pretty good approximation of how my browser looks at the end of a given day.

image

Totally lost in my tabs is a good way to trace my path through coding horror. Imagine that my tabs represent a lengthy night of researching for a term paper, or digging into news on a company for deciding whether to invest my life savings in an IPO, or case research that could make sure that a defendant doesn’t get off on a technicality.

This idea really hit home with me and I started typing about it. 4 hours and one thousand words later, I had a vision for what for lack of a better term I called a Streamcatcher. Shortly after doing this, I received a newsletter from Infoq.com pointing to an article about stream-oriented User Interfaces (was it really back in July when I first started doing this). My jaw dropped. It was as if someone had read my vision and written an article about it. Further research revealed that the idea of a Stream-oriented UI has been around for quite a while now.

I started making a basic object model for an application that could visualize your browsing history as a graph of nodes and stumbled across a WPF panel for displaying a graph of objects. The next weekend I had a prototype browser that built the graph as you browsed.

Anyway enough blabbing from me. Here is the original prototype I made so that you can get a picture of where we’re going. Ignore the ribbon. It doesn’t do anything. I was just experimenting with it and never bothered to take it out. Also the network graph component that I’m using will expire in 30 days after you first use the app, making the application useless. There is no way to save your graph. Right now it’s just a prototype. I’ll be uploading the code to the Codeplex project and starting the new codebase there as well.

http://cid-2221dc39e0c749a4.skydrive.live.com/embedrowdetail.aspx/WPFSamples/FlowSetup.zip

To get started, place your mouse over the green dot and click on the button that appears. That will take you to google.com to start searching. An interesting search term is “flow psychology” (no quotes). I posted a video showing how flow works in an earlier post.

Now if you’ll excuse me, I have 40 tabs of Coding Horror to read.

Refactoring to Patterns: WPF Edition

To some it may appear that I have abandoned client side development for Azure. Nothing could be further from the truth. As I’ll tell anyone who will listen, I’m just like a kid who’s opened his presents on Christmas and found a new toy to play with. After playing with the new toy for a while, eventually I’ll remember my old favorite and start playing with it again. (The real fun comes of course when I start playing with both together). It’s not a Buzz Lightyear vs. Woody…it’s more like Megatron vs. Galvatron. Anyway, I had to come back to Megatron at some point or another. And a recent thread within the WPF Disciples mailing list gave me that impetus. I’ve recently realized how effective refactoring can be for getting working code out rapidly while still addressing maintainability. My experiments with refactoring resulted in a technique I like to call "context sensitive architecture."

A Practical Application

I’m not a huge fan of contrived applications, but sometimes we do what we must. This won’t be one of those times. Let’s say you have an application that could provide a rich view of your digital life and how that digital life is connected. Let’s say for now the application could show contacts and bookmarks. Finally, lets say that the application wants to allow the user to add and edit contacts and bookmarks. How do you enable these scenarios? One way would be to create a CreateContactControl, an EditContactControl, a CreateBookmarkControl, and an EditBookmarkControl. I guess we want to allow the user to View their contacts and bookmarks. Now we have to add a ViewContactControl and a ViewBookmarkControl. What happens when we add RSS Feeds and Podcasts to the mix? Now we have to create six more controls and integrate them into the system. What’s worse is that the main app has to know about each and every control in order to display them at the appropriate time. Of course we could use plug-in model to alleviate some of this pressure, but this could end up generalizing your application to the point where it is little more than a shell. There’s nothing necessarily wrong with that, but I still think there’s a compromise between the two extremes. Sometimes that compromise isn’t very obvious. Hence, we use refactoring and iterative development to discover the compromise.

The First Iteration

The first iteration of a project should be used to implement what is called a "vertical slice" or two. This will allow us to realize the benefits of Agile development with the first delivery. Getting working software into the customer’s hands quickly provides a compelling argument in favor of Agile development. I would actually recommend that you start with a minimal core team (2-3 members) for the first few iterations, this will enable you to minimize the overhead due to collaboration as the team takes its first steps into a new domain. It will also allow a few patterns to emerge before ramping up the velocity. Because you’re targeting a smaller amount of functionality for the iteration, you might want to do a shorter iteration. I think two weeks should be adequate.

Before we go any further, let’s try to visualize this app with a pair of its scenarios: "Add a Contact" and "Add a Bookmark". The "Add a Contact" story is very simple: "As a user of the application, I want to be able to enter information about a contact for later retrieval and viewing: his or her first and last name, and email address." Likewise the "Add a Bookmark" story is equally simple: "As a user of the application, I want to be able to store information about a bookmark for later retrieval and viewing: the URL, and title of the bookmark."

Based on these stories, we have identified two entities for our domain model: Bookmark and Contact. Here is the Bookmark:

   1:  using System;
   2:   
   3:  namespace Flow.Model
   4:  {
   5:      public class Bookmark
   6:      {
   7:          public Uri Address { get; set; }
   8:          public String Title { get; set; }
   9:      }
  10:  }

The Bookmark is very simple, consisting of a Uri and a Title. We will probably identify more information that would be interesting to capture for a bookmark in a later iteration. For now, we want to get working code into the hands of our stakeholders as quickly as possible. Our second object of interest is the contact:

   1:  using System;
   2:   
   3:  namespace Flow.Model
   4:  {
   5:      public class Contact
   6:      {
   7:          public String FirstName { get; set; }
   8:          public String LastName { get; set; }
   9:          public String EmailAddress { get; set; }
  10:      }
  11:  }

Let’s make a pair of controls for creating new bookmarks and contacts. Following the WPF developer – designer workflow, I will make the first pass on the UI simplistic and straightforward (relying on my designer to beautify it later).

After a few minutes in Blend, followed by some cleanup in Cider, I came up with a rather straightforward, minimalistic UI with the primary elements defined for optional elaboration by my designer:

image

image

Now that I have a way to create contacts and bookmarks. I should allow the user to view them. That’s easy enough. Let’s make a ListBox that shows the collection of contacts and another pair of controls that are read only. Rather than worrying about persistence at this point we’ll just store the information in memory.

So What Next?

We’ve delivered some basic functionality to our customers. More importantly, we have started the first path in our journey together. I will be placing the code on Codeplex. In addition I will be posting a screencast of me writing this code (once I figure how to get Camtasia to co-operate with me). This is something I’ve wanted to do for quite a while now. I just couldn’t find a project that I was compelling enough that would be able to grow from a very simple solution to a very interesting WPF application. I will reveal more about it over the upcoming weeks; in the process documenting the evolution what I feel is a very interesting application. Tune in for more info.

Starting the New Year With a Bang!

Yes I know it’s February already, but this should show even more how big the start of this year has been for me. First and foremost is the big announcement that the new year brought.

MVP_FullColor_ForScreen

First and foremost, I’ve been named an MVP in Client App Development (for my community contributions with WPF). This is an incredible honor for me. In addition to the title, being an MVP provides me an opportunity to have better interaction and feedback with Microsoft especially with regards to my specialization. According to the program guidelines, the award is for my past activities and I am not required to do anything else.

However, I want to leverage this opportunity to the fullest and will continue my community contributions going forward, both with regard to WPF and Silverlight as well as with Windows Azure.

USAltNET

Second, as an organizer for our local Alt.NET User Group, Indy Alt.NET, I’m excited about a few recent developments with the group. Chief among those being named an official INETA group – something that surprised me seeing that there was already an INETA group in the Indianapolis area. We are coming on our first anniversary and have seen our attendance stabilize at around 25 per meeting. With almost a year under our belt we have sat down and started a few initiatives.

One major decision will be to incorporate as a non-profit organization (an idea we had thrown about for a while but were too busy with day to day operations to act upon). This action will allow us to apply for grants and begin some community outreach initiatives that we are all excited about. It will also make us more attractive to potential sponsors as certain donations to us will be tax deductible.

Another initiative has been a marketing and sponsorship drive. We are trying to grow organically, but we have noticed that we have a chicken or egg scenario. Therefore, we are pushing our growth on multiple fronts. So far we are getting good feedback from our efforts.

Our biggest initiative about which we are all very excited is planning for a local conference. More on that later 😉

SEP-logo

But wait there’s more! I just finished my first year with my current employer, Software Engineering Professionals. Management announced a number of initiatives here that are pretty exciting for me. I can’t necessarily talk about them right now, but it reaffirmed my decision to come here. I can honestly say that I have grown dramatically since I’ve been here. It is an amazing place to work, and I’m excited to see what the future has in store.

SEP-logo

Finally, my family is counting the days until our latest addition is expected to arrive.

Like I said, this year is starting off with a bang…and there’s more to come. I’ll keep you posted with new developments.

Announcing Azurecoding.net

I am head over heels about Azure and the Live Services. I love it so much that I’ve gone ahead and registered http://www.azurecoding.net Depending on your pronunciation of Azure, you might chuckle at the name. So what are my goals for the site? I want Azure Coding .NET the place to go for news, articles, tutorials, and discussions about Windows Azure and the Live Services including Live Framework, SQL Services, and the .NET Services (we might even talk a little bit about how “Oslo” fits into the picture). I’m going to fire off the first few volleys with some in depth talks about Live Framework, and .NET Services.

Like desktop Windows development, there are too many specialty areas within the cloud development ecosystem for one person to be a master of them all. So I’ll be bringing some friends along. No matter how compelling the topic is, a website is only as good as its community. I will definitely look for ways to engage the community. Look for more on that later!

PDC 2008 All Good Things…

Well it’s done! What a wild week it has been. From the announcement of Windows Azure, and the .NET/SQL Services to the new features of Windows 7 to upcoming features in WPF/WCF/WF 4.0 and let’s not mention Oslo and “M”. Thank you everyone for following along with my trip, both here and on Twitter. It’s been a blast. I got to finally meet some people I hadn’t met before in person. And of course I met a lot of new names and faces.

PDC 2009 has been announced and I highly recommend that whether by hook or by crook, you find your way down there. Yes you can view all the sessions and information online. But you can’t get the Windows 7 bits yet. You also can’t get a live services/azure key yet. You also miss out on the experience of being with a crowd of smart developers congregating in one place. And of course there’s no substitute for actually being in the room when Ray Ozzie says “…so we’re pleased to announce Windows Azure.”

Personally, I’m extremely excited to finally get my hands on the Live Mesh (now Live Framework) SDK. I have a compelling story to tell with the mesh. And I think it just might change the way you look at your computer! Anyway…enough about my plots for world domination. Plain and simple…PDC is all about catching the wave of new technology and riding it to success. There is a ton of content on the web discussing the “Long Tail” of software development. Jumping on the new tech announced at PDC will help you stay ahead of the long tail. It’s somewhat risky, because we all know what happened to WinFS (rest in peace). But on the other hand, picking the next WPF (even if that happens to be literally the next WPF), can be a very rewarding experience. Ask Josh Smith, and other WPF luminaries.

Hopefully, everyone is stoked and excited. And you’ve already run over to the Azure website to signup for your keys. If nothing else, you’ll get a free web host for the duration of the CTP.

PDC 2008: Mesh Services Architecture and Concepts

Okay…I couldn’t live blog the whole thing…there’s a lot to take in…but here’s the gist. Mesh takes care of a LOT of complex stuff so you don’t have to be concerned with it.

3:00 Introduction:
       
Mesh is a concept whose time has come
        It takes the Windows platform to the next level
        Allows windows to take advantage of the cloud and the many devices a user has
        This talk mostly about Mesh Architecture
3:04 Agenda
       User Experiences
       Concepts
       Architecture
       Planning and Deployment
       Implementation
       Operations, Experiences, Lessons learned
       Future
3:05 Quick Demo Using Mesh
3:10 Key Capabilities
        Provisioned State (Accounts)
        User-data storage (including replication and synchronization)
        Communications and presence (P2P when possible…fall back to relay when not)
        Notifications (Single channel for asynchronous push)
3:13 Provisioning in the Mesh
        Identity is provisioned during web signup
        Device provisioned during software installation
        Device claim – relationship between user and device established
3:14 REST in the Mesh
        Common metadata for all resources (Uri, LastUpdateTime, Etc.)
        Resource lives within collection (scope for grouping resources and tracking changes)
        Both resources and collections are represented as feeds and items
        Links allow navigation from one resource to another.
3:17 Provisioned State Services
        Account Service is a “Facade” for accessing accounts, devices, and apps.
        The client provides a local cache.
3:18 Folder Synchronization in the Mesh
        Items in data feed represent files (files are the resource)
        A data feed mapping tells Mesh that a given device wants to synchronize with a given feed
        Permission scope defined on mesh object for sharing feeds
3:21 Understanding FeedSync in the Mesh
       Bi-directional replication provided through schema and semantics.
3:23 Getting really deep into how Mesh client is implemented using the Live Framework
3:27 Architecting the Mesh Services for Scalability
       Primary scenarios for scalability concerns
       Startup
       Resource change (initiator)
       Resource change notification (recipient)
       Content replication
          This can take advantage of P2P scenario
3:31 Scale-out strategy
       Partition by user, device, and mesh object
       Use soft state to minimize i/o load
       leverage http semantics for caching, change notification, and incremental state transfer
3:35 How to Partition resources
       Every resource has a stable canonical URI based on its resource identifier
       Mapping a resource id to its home DC requires a lookup in a replicated database
3:37 General Design Principles
       Use commodity hardware
       Partition for scaling out
       Loose coupling across roles
3:38 Deployment
        2 Dual Core sockets
        8 GB RAM
        2TB HDD
        Windows Server
        New machine come on line…fabric is copied to it and it joins the cloud
3:43 Scale Unit Layout