Edgenet to Provide Google with High-Quality Product Data

by Administrator 14. October 2010 01:40

Yes, I dropped off the map for a while.  A long while.  Friends and acquaintances from the community asked what I was doing.  I can now begin to talk about what I’ve been working on.  There are more announcements to come.



“Ezeedata Search” (as the marketing folks have chosen to call it) is, I suspect, one of the largest Silverlight 4 business application projects in production right now.  My team worked outrageously hard, learned new technology very quickly, and generally overcame ridiculous challenges in order to bring this effort to market.  I can’t show you screenshots yet of what Real Time Data Quality looks like, but it’s a challenging system to bring into an internet deployed smart client application.  There should soon be more official press releases and possibly screenshots or screencasts if I get permission.

Now I’m going to play video games and get some rest.


Speaking at the Chicago Silverlight User Group

by Administrator 3. October 2010 18:22

This coming Wednesday, October 6th I’ll be talking about Silverlight and MEF at the Chicago Silverlight User Group.  I will be covering some advanced topics, so even if you’ve seen the usual 100 and 200 level stuff with MEF it might be worth your time to come out this week.

Details and registration can be found at http://chicagosilverlight.eventbrite.com/ 

I’ve been having some questions about when I’ll get back to Shinto, or AGT, or my Great Features for MVVM Friendly Objects series.  This is the last week of my Infamous Deathmarch so I hope to slowly return to normalcy this fall.


Speaking at the Rockford .NET User Group

by Administrator 26. September 2010 16:07

In just a couple of days I’ll be presenting “What’s new in Silverlight 4” at the Rockford .NETR User Group in Machesney Park, Illinois.  You can find details here: http://rockforddotnet.net/UserGroup/Meetings/MVVM---The-What,-Why-and-When-(1).aspx .  Yes, the URL does not match the title.  Good think I keep at least four presentations on my laptop at all times.


Advanced MEF at St. Louis day of .NET

by Administrator 16. August 2010 17:14

This weekend (Saturday morning) I'll be giving an advanced MEF talk at the St. Louis day of .NET. You can find details here I hope to see some familiar faces there!

When last I looked, this was the only MEF talk at the conference, so I'll try not to suck.



by Administrator 23. July 2010 02:02

Next week Thursday in Grayslake, Illinois I’ll be speaking on one of my favorite new topics, in this case MEF !

You can find directions and register here:


I have a great deal of both entry-level and advanced MEF content and how much we get through will depend upon the attendees.  I’ll be using mostly Silverlight and WPF to demonstrate different bits of MEF-Fu though there may be some surprises too…


I’m Back

by Administrator 19. July 2010 04:21

I was out of the country last week.  I managed to not touch a computer or Smartphone of any kind for eight full days.  I even made my wife use the check-in kiosks in the airport.

To everyone who contacted me as part of their recruiting efforts, or were seeking to learn the identities of the MSDN subscription winners, or had technical presentation related questions, I apologize.  I don’t advertise the fact that I won’t be home on the same blog where you can find pictures of my toys ;).

This is only the second time my wife and I have been able to get out together for a no-kids vacation. 



Great Features for MVVM Friendly Objects Part 2 – Change/Dirty Tracking

by Administrator 6. July 2010 01:33

It’s often very useful to know when an object we are editing has Changed.  The most iconic example is the “*” that used to appear next to the title of Word documents once you’d made the first change no matter how small.  It’s not an unusual request that a “Save” button be disabled until the User has made a savable change.  This is often referred to as an object being Dirty.

This article is part of a series about useful MVVM friendly features for your data objects and favoring composition over inheritance.  You can read the other parts:

Dirty Aware

Now that we’ve introduced the idea of Property Change Behaviors, it’s easy for us to flag an object as having changed when we set any property value.  Let’s refer back to the BBGrill object in the Metro BBQ sample application.  I find it’s useful to standardize the HasChanges/Dirty state using an interface. 

/// <summary>
/// Capable of storing and notifying Dirty/HasChanged state
/// </summary>
public interface IDirtyAware
    bool IsDirty { get; set; }
    bool SuspendChangeNotification { get; set; }

We can now author a new IPropertyChangedBehavior that deals with IDirtyAware instances and sets their IsDirty flag to true whenever a property value changes.

public class DirtyPropertyBehavior : IPropertyChangedBehavior
    /// <summary>
    /// </summary>
    /// <param name="owningInstance"></param>
    public DirtyPropertyBehavior(IDirtyAware owningInstance)
        : this(owningInstance, new List<string>() {"IsDirty"})


    /// <summary>
    /// </summary>
    /// <param name="owningInstance"></param>
    /// <param name="exclusions"></param>
    public DirtyPropertyBehavior(IDirtyAware owningInstance, List<string> exclusions)
        _owner = owningInstance;
        _propertyExclusions = exclusions;

    IDirtyAware _owner;
    List<string> _propertyExclusions;

    /// <summary>
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <param name="owningInstance"></param>
    /// <param name="oldVal"></param>
    /// <param name="newVal"></param>
    /// <param name="propertyName"></param>
    /// <returns></returns>
    public bool PropertyChanged<T>(object owningInstance, T oldVal, T newVal, string propertyName)
        if (!Object.Equals(oldVal, newVal) 
            && !_propertyExclusions.Contains(propertyName)
            && !_owner.SuspendChangeNotification)
            _owner.IsDirty = true;
        return true;

Note that we can easily provide the ability to exclude certain properties from setting IsDirty, which is very useful for the IsDirty property itself.

Obviously we could put this functionality right inside the property setters but we want to make it easy to add/remove behaviors to objects.

Dirty Grill

Going back to the Metro BBQ sample application, I can now make BBQGrill implement IDirtyAware and also use the DirtyPropertyBehavior to flag when any change has been made.

public class BBQGrill : BindableType, INotifyDataErrorInfo, IDirtyAware
    public BBQGrill()
        _changeBehaviors.Add(new DirtyPropertyBehavior(this));

Now, this is useful as we can key business logic off of the IsDirty property, however we can also bind to it in the UI which is just as useful.  Recall the Ideal Grill survey page from Metro BBQ.  We wanted to only enable the Save and Rest buttons once the user had made changes.  Now it’s easy to do so:

 <Button Content="Submit" Margin="10,0,10,0" IsEnabled="{Binding Grill.IsDirty}" />
 <Button Content="Reset" Margin="10,0,10,0"  IsEnabled="{Binding Grill.IsDirty}" />

This gives us the effect that we want in the UI for any property with extremely little code.

Screen default state:


After changing one property:


Because of the way we structured Property Change Behaviors we just got a Binding-friendly “is dirty” behavior on all properties of the BBQGrill object.  Once we wrote the DirtyPropertyBehavior we got this essentially for free on all properties without writing extra code for every property.

Suspend Notifications

You may already be thinking of situations where you’d like to temporarily turn this property behavior off.  For example, you might be populating BBQGrill object values from a WCF service and obviously invoking property setters in that situation should not instantly mark the object as Dirty or this feature won’t be very useful.  You may have noticed that the IDirtyAware interface included a SuspendChangeNotification property and that the DirtyPropertyBehavior pays attention to this and does not set IsDirty when SuspendChangeNotification is set to true.  This solves the re-entrant problem but we can do a little better in terms of the developer experience around this code using a context class.

/// <summary>
/// Enable nice using(){} semantics for setting property values without firing Dirty state behaviors
/// </summary>
public class SuspendDirtyContext : IDisposable
    public SuspendDirtyContext(IDirtyAware target): this( new List<IDirtyAware> { target } )

    public SuspendDirtyContext(IEnumerable<IDirtyAware> targets)
        _targets = targets;
        int index = 0;
        _targets.ForEach(d => 
            _previousValues[index] = d.SuspendChangeNotification;
            d.SuspendChangeNotification = true;
        _previousValues = new bool[_targets.Count()];

    IEnumerable<IDirtyAware> _targets;
    bool[] _previousValues;

    public void Dispose()
        int index = 0;
        _targets.ForEach(d =>
                d.SuspendChangeNotification = _previousValues[index];

In C#, classes that implement IDisposable can be used in using() blocks.  While we’re not really getting rid of any resources here the syntactical sugar is too good to pass up. This SuspendDirtyContext allows us to write nice readable code like the following:

var bbqGrill = new BBQGrill();
using (var ctx = new SuspendDirtyContext(bbqGrill))
    //... set initial values

The using() block in C# winds up creating try/catch/finally semantics in IL, so even if something causes an exception to be thrown our object state won’t be wonky outside of this scope.  As you can see the SuspendDirtyContext can also handle more than one IDirtyAware instance. 


Knowing when a user has made a change to a data entity through the UI is a commonly requested and useful feature, and implementing it can be pretty easy with the right design of your data entities.  Using the Composition approach makes it very easy to turn this feature on and off for different objects or even different instances of the same type depending on your needs. 

There are still situations that can be easily supported using the same techniques we’ve already demonstrated and these will be explored in the following articles. 


I&rsquo;m going to give you a Visual Studio 2010 Ultimate MSDN Subscription

by Administrator 5. July 2010 02:10

I have in hand a couple of one year MSDN Subscriptions with Visual Studio 2010 Ultimate.  Never you mind where they came from, but they didn’t fall of the back of a truck, they are legitimate. 

These are not for me, they are for YOU.  However, there are only two of these and according to my quick Twitter poll, a lot more than two people who’d like their own MSDN Ultimate.  Therefore, I pose to you a very simple contest.  Leave me a comment or send me an email telling me why you should get a subscription.  I will choose the winners late this week.

{Edit: I should be clear: I’m looking for community influencers here.  Tell me how this prize will touch more lives than just your own}


2010 Microsoft MVP

by Administrator 2. July 2010 01:24

I am honored to be re-awarded the Microsoft MVP award in the Client App Dev competency.  As others have pointed out, re-awardees have to be vetted just like new awardees – no coasting!  I couldn’t have achieved this without all of you out there who keep reading my blog and inviting me back to your user groups, code camps, and conferences.  I have big plans for the next year so please keep coming back!




MEF for Windows Phone 7

by Administrator 25. June 2010 03:52

Given the momentum behind MEF at Microsoft and the fact that MEF has shipped in the box with Silverlight 4, you may find it somewhat disappointing that MEF is not available for Windows Phone 7.  Due to low level differences in the CLR for Windows Phone 7, you can’t just grab MEF from Codeplex either – read on to see the solution.

{Edit: I later posted the binaries http://www.damonpayne.com/post/2011/03/01/MEF-for-Windows-Phone-7.aspx }

The Goal

Given the Marketplace restrictions, we know that our application code must go through a QA process and be signed in order to be deployable to the Windows Phone 7 (henceforth The Phone, or WP7). It’s not surprising then that the popular Silverlight Dynamic Recomposition techniques using MEF and downloaded XAP files won’t work.  However, it’s still incredibly useful to be able to use DeploymentCatalog and friends to wire together components in an application.  Getting this scenario working on The Phone is how I’m defining success for now.

Getting MEF to Build and Run

Prior to .NET 4 and Silverlight 4 shipping MEF has been available in preview form on Codeplex.  I was surprised that, being a daily reader of Silverlightshow.net, I hadn’t already seen an article submitted by someone who had built MEF for Windows Phone 7.  Now I know why.

Trial 1 – Building MEF Preview 9 as a Silverlight 3 Project

Many Silverlight 3 assemblies will turn out to just work on The Phone.  It seems reasonable that the first thing to try is to get MEF Preview 9 from CodePlex.  You can build this as a Silverlight 3 project and then reference the binary output from a WP7 project.  Trying to use DeploymentCatalog immediately blows up at runtime though.  That would have been too easy.

Trial 2 – Referencing MEF Preview 9 as a Silverlight 3 Project with Source

Rather than just building and referencing System.ComponentModel.Composition and System.ComponentModel.Composition.Initialization as assemblies, I thought I’d add the source projects to my test solution and step through to see what was going on.  It could always be something simple and obvious.  I was getting some interesting MissingMethodException and MethodAccessException behavior so as feared this was likely going to involve source code modifications to get it working, if it was possible at all.  I moved on to the next logical choice.

Trial 3 – Building MEF as Windows Phone 7 Class Libraries

At this point I assumed some low-level binary incompatibility or missing Type was the issue so I decided to create two new WPF class library projects and add the respective MEF source files to these.  Building MEF using Windows Phone 7 Class Library as the project type would immediately show me any issues with base class library parity.   At this point I was confronted by three major issues I was previously unaware of.

No System.Reflection.Emit

I was always extremely happy that SRE was included in Silverlight, so I was a bit surprised to find it missing from The Phone.  Sure, we never had it in Compact Framework development but The Phone is a much more heterogeneous platform compared to the giant universe of Windows CE/Windows Mobile hardware.  This spells doom for some of my more advanced Silverlight development scenarios, and for certain MEF features as well.  MEF uses SRE to create dynamic implementations of interfaces for Metadata – very handy for Lazy Imports. 

I have a reasonably easy workaround for the Import Metadata issue, but eager to get my main success scenario working I commented this feature out for now and moved on.

No IQueryable

The MEF code uses a fair bit of IQueryable internally.  Not being familiar enough with LINQ Expression hacking I can’t fathom why this was left out.  Performance implications?  Required Reflection Emit?  I don’t know.  Nonetheless, this code had to be changed in places like TypeCatalog, AggregateCatalog, and the ComposablePartCatalog base class.  Until I at least got this to compile I wouldn’t know if IEnumerable would work as a surrogate for IQueryable or not.

{No IQueryable http://social.msdn.microsoft.com/Forums/en-US/windowsphone7series/thread/79858a29-4db0-460d-9a75-3630211a28fb/ }

No Dynamic Assembly Loading.  Period.

Silverlight XAP files are packaged with a Deployment Manifest that makes it easy to enumerate the assemblies included in a given XAP file.  In the Full versions of Silverlight you can use these AssemblyParts to load the assemblies and do useful things like add them to an AssemblyCatalog for MEF.

In their Zeal to prevent you from somehow loading code onto The Phone that had not gone through The Marketplace, you can’t load assemblies by name using this technique or any other technique.  Unfortunately this even includes assemblies that are hard-referenced by your WP7 Application.  What the harm would be in allowing developers to get a handle to all the assemblies that are hard-referenced is beyond me but this one is a showstopper.  Or is it?

We Can Continue, but Should We?

Suppose we can keep going.  Is MEF worthless in the Windows Phone 7 scenario given these limitations or is there still value to be had?  MEF is about Composition, Isolation, Separation, and Extensibility.  MEF is about programming against abstractions and making it easy for third parties who are unknown at compile time to extend your applications.  While some of these benefits cannot be realized given the WP7 limitations there are still meaningful benefits.

  1. Suppose you are developing frameworks and using MEF as your mechanism of wiring up Abstractions to their Implementations.  If you want to share any code with The Phone, it would suck to not at least be able to use MEF to map “IWidget to DefaultWidget”.  Programming against abstractions is always good.
  2. You may simply prefer the Import/Export programming model to alternatives like Factories and Service Locators.  Doing these things manually can take a lot of code.
  3. You may be used to ImportMany semantics, which is not a common feature in IoC containers that I know of.
  4. Microsoft may loosen up the WP7 deployment story in the future and you want to be ready.
  5. You love MEF and you have a Man-crush on  Glenn Block and you want to achieve Universal MEFness

The Current Workaround

For my part, I am working on frameworks that I’d like to recompile for Windows Phone 7, and I’ve become very accustomed to the great programming model MEF enables.  I’m NOT going to manually register every single Type I use to get around the DeploymentCatalog issues though.  Given that we can’t load assemblies by name, is there any compromise we can make?  Yes there is.

Since we can only hard-reference assemblies for Windows Phone applications, we can cheat and get a handle to each assembly we want to participate in Composition by using any Type from each assembly.  By then modifying DeploymentCatalog to add an additional constructor we can at least run some sample code and see what’s working and what’s not.  I went ahead and created a Mobile version of the Metro BBQ example I’ve been using lately.  I have an entry point application and two module assemblies and I’d like to to use MEF to glue them all together.


In the entry point application there is a simple UI that displays Gas Grills and Charcoal Grills, and I’d like to create a simple ViewModel that gets populated with IGrill implementations via MEF Catalogs.

namespace MetroBBQ.Mobile
    public class ShellViewModel : INotifyPropertyChanged
        private IEnumerable<IGrill> _AllGrills;

        public IEnumerable<IGrill> AllGrills
            get { return _AllGrills; }
                _AllGrills = value;

        public event PropertyChangedEventHandler PropertyChanged;

        protected void OnPropertyChanged(string propName)
            if (null != PropertyChanged)
                PropertyChanged(this, new PropertyChangedEventArgs(propName));

Now using some bootstrapper types from each assembly along with my DeploymentCatalog modifications, I create a CompositionContainer, and give it all a try.

private void PhoneApplicationPage_Loaded(object sender, RoutedEventArgs e)
    var shimTypes = new List<Type> { typeof(MetroBBQ.Mobile.GasGrills.Bootstrapper), typeof(MetroBBQ.Mobile.CharcoalGrills.Bootstrapper), GetType() } ;
    var deploymentCatalog = new DeploymentCatalog(shimTypes);
    var container = new CompositionContainer(deploymentCatalog);
    var vm = new ShellViewModel();
    DataContext = vm;

Sure enough, I’m now able to Compose Parts just like my MEF experience on other platforms.  There are a LOT of other scenarios to test but I’m encouraged by this initial success.  My ViewModel gets populated with IGrill implementations from two other assemblies in my Windows Phone 7 application.



What do you think, dear reader?  Is it worth doing more testing or shall I add this to the collection of forgotten novelties on my shelf?  Would you like the source code?  Is this worthy of MEFContrib? Leave me a comment!  For my part, I’m happy to be able to continue my MEF experience on this new platform.


About the author

Damon Payne is a Microsoft MVP specializing in Smart Client solution architecture. 

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