The keynote at MIX09 is almost over and Expression Blend 3 has been announced !

Go ahead and grab this new version from the Microsoft Expression web site.

A video is also already available on Channel9, where Unni Ravindranathan takes on a tour to demonstrate the new features of Blend 3. I just finished watching the show and here are my notes:

• Blend3 supports Silverlight3 but there is more than that: lot of new functionalities to improve the user experience and the productivity
• Goal: be more creative inside the tool
• In Blend2, it was sort of complicated to select objects, particularly with nested containers. With Blend3 it’s a lot easier, we no longer have to navigate inside the objects explorer. Just click and you’re done
• New features to manipulate the gradients : we can manipulate the gradient stops directly from the artboard
• Supports for shaders : the assets panel now contains a “shader” category – drag’n'drop on the artboard and you’re done
• Supports for projections in Silverlight3, new category from the property grid to edit them
• Import from Photoshot and Illustrator functionality !
• XAML Intellisense (oh my god !)
• Team Foundation Server support
• Sample data source generation inside Blend3 (Blend is able to generate sample data such as texts and images)
• New features: behaviours that can be drag’n'dropped from the assets panel on the artboard to attach a piece of code to a visual element (could be used to start an animation for example)
• Easing functionality when working with animation: define elastic, cubic, exponential animations (I think designers are going to have some fun)
• New extensibility points to the Editor: custom adorners, custom panels, extend property grid, etc.

Here are some screenshots I just took running the preview on my machine. I think Blend3 is going a major step forward in the Expression Studio 3. Don’t wait a second to play with it !

Welcome to Blend3 !

The new assets panel

Easing functionality

XAML Intellisense !

Day 1 keynote will take place at 9:00 AM PST (5:OO PM in France :p) and we’re all excepting big announcements about the future of WPF, Expression Blend and Silverlight.

It’s possible to follow the keynote online at live.visitmix.com !

Apparently, some of the CTP bits that will be anounced during the keynote are already available such as Silverlight 3 SDK. Can’t wait to see the keynote

If you find yourself:

• having huge .xaml.cs code behind file
• using event handler (such as Click…) everywhere
• tweaking TreeViewItem (using ItemContainerGenerator for example) to manipulate a TreeView
• having tons of IValueConverter
• … then MVVM might come to the rescue :p

What MVVM can offer?

• a clean and well defined separation between the Model and the View
• the possibility to easily leverage the power of WPF: databinding, commands, validation, and more
• a code that is testable
• an organization that facilitate the workflow between designers and developers
• minimalist code-behind file (which leads to testable code)
• facilitate the deployment of an application in multiple environment (WPF / Silverlight)

How is that possible?

Here is a part of the introduction of John Gossman:

“In simple examples, the View is data bound directly to the Model. For example, a boolean in the Model can be data bound to a CheckBox, or a string field to a TextBox. In practice however, only a small subset of application UI can be data bound directly to the Model, especially if the Model is a pre-existing class or data schema over which the application developer has no control.
The Model is very likely to have a data types that cannot be mapped directly to controls.  Finally we need a place to put view state such as selection or modes.
The ViewModel is responsible for these tasks.  In this latter role the ViewModel contains data-transformers that convert Model types into View types, and it contains Commands the View can use to interact with the Model.”

• The View has the associated ViewModel set as its DataContext so that the View can easily data bind to ViewModel properties
• The ViewModel reflects its changes to the Model by calling appropriate methods on the Model
• The ViewModel exposes ICommand that the View data bind to, in order to execute actions
• The Model signals its changes to the ViewModel by raising events

What are good resources to start working with MVVM?

• Karl Shifflett started a series about MVVM, you can find his work here.
• Karl and Josh Smith wrote a very nice application that uses MVVM pattern. Moreover the application contains also information about internalization support. Check out the CodeProject article here.
• Karl wrote an article about a very important concept: user input validation. This is the first article of his new MVVM series.
• WPF architect, John Gossman wrote a series of blog post about MVVM on his blog. An introduction to MVVM is available and a good point to start.
• Josh Smith wrote an excellent tool, Crack.Net which is built using MVVM. Crack.Net is hosted on CodePlex, and studying the source code is a very good manner to understand how stuff fits together in the MVVM world.
• Josh Smith wrote an article about applying MVVM concepts to the WPF treeview. If you must work with a complex treeview, then you MUST read this article.
• Marlon Grech wrote an article about ICollectionView. ICollectionView is a useful interface that can be used in ViewModel classes to keep track user selection

If you never heard about MVVM, or never take the time to look at it, I suggest you to take a look at some of those links. Trust me, the investisment worth it !

“When I installed VS.net express 2008, I was happy because I thought that with WPF I’ll be able to build nice UI. Unfortunately, I have the felling this is more like a source of problems… I spent several hours to fill a ListView with some data and the result is dirtier than with WinForms. The designer in VS.net sucks and  many controls are missing. It was so simple before…”

I wanted to give my point of view about that kind of reasoning because a couple of months ago, I think I had more or less the same… So, what makes WPF so different ? Or why I cannot just use my WinForms background and start to build wonderfull apps ?

I think that WPF is more than just a new framework or new classes. It is more than that because when you work with WPF, you have to change the way you think and design your apps.

• You have to change the way your work with controls because you can apply new Style and Template to them so that you can completely change the way they look
• You have to change the way you design your apps because of DataBinding and Commands
• You have to… forget almost every things you already know, and be ready to learn again !

If I can give an advice, I would suggest to read a good WPF book. A couple of weeks ago, I finished to read WPF unleashed, by Adam Nathan ¹, and I really think that having this kind of the book is the right way start working with WPF. A lot of cool website are also full of interesting resources, CodeProject is maybe the one that I like the most.

To conlude, I would like to give a quick example ².

Imagine you’d like to build an application to browse a catalog of products. For each product, you need to see the name of the product, its designer, a description and an image. You also would like to have navigation build around the use of 2 arrows to browse products:

How could you achieve this ? You might think about several ways to do it. The point is that you can do this by only using a ListBox and changing its style ! Isn’t amazing ? Go ahead and check the full video at http://sessions.visitmix.com/.