MVVM in the Real World
I presented my talk “MVVM in the Real World” at the October meeting of the Twin Cities .Net User Group. Considering that it was my first “real” technical presentation that wasn’t just to coworkers it seemed to go pretty well. Some good questions were asked and I hope I helped clear up some problems people were having when trying to use MVVM in a real world project.
I mentioned during the talk that you should be careful when searching WPF & Silverlight blogs to try to solutions to problems you run into. A lot of people have started to love the XAML, which is awesome, but not all of their advice is good. Although quite a few have slowed their posts lately here are some of the WPF & Silverlight blogs I follow:
- Josh Smith – The guy that wrote that MSDN MVVM article and book everyone talks about.
- Dr. WPF – I can’t recommend his ItemsControl: A to Z series highly enough.
- Bea Stollnitz – I refer people to The power of Styles and Templates in WPF so often I have the post number memorized.
- Karl Shifflett
- Jaime Rodriguez
I also mentioned Rob Eisenberg’s presentation at Mix 10, Build Your Own MVVM Framework. It’s an excellent presentation if you want to dive deeper into MVVM and see some of the tools I mentioned that are used to solve common issues people run into with MVVM.
I hope the presentation and this post were helpful, you can get the slides here.
A Canvas allows you to precisely position elements within a region. This is also one of the few panels that allows elements to easily overlap (the other I know of is the Grid). In many cases you might think you need to use a Canvas, you don’t. Much like 
The DockPanel allows you to dock UI elements to the edge of the panel while letting another element fill the rest of the space. It is a great replacement for most uses of the Grid because of its lighter weight. The DockPanel is one of my favorite panels for larger scale layouts and should become one of yours as well.
The Grid is probably the most powerful of all panels. It is also one of the heaviest in terms of CPU and memory usage. That isn’t to say that you should avoid using a Grid if you need one, just don’t use it in every place you need a panel if another type of panel (other than Canvas) will work just as well. With a Grid you can make any layout you could make with HTML tables. You can size columns and rows either based on their content (Row Height/Column Width=”Auto”) or based on what the Grid is contained in (Row Height/Column Width=”*”).
The StackPanel is the bread and butter of many layouts and especially within control templates. Basically the StackPanel stacks items either vertically or horizontally. One thing to be careful of: the StackPanel is unconstrained in the direction it is stacking, e.g. you could stack buttons right off the screen and even if you add scrollbars depending on the visual tree they may never appear.
The UniformGrid is an interesting control. It lays out elements in as near to a square grid as it can without having to specify the number of rows or columns within it. The most common use I’ve found for this is as the ItemsPanel in an ItemsControl. Say you want all of your items displayed in two equal columns. All you have to do is tell the UniformGrid you want two columns and it will make two equal columns and fill the items into however many rows are required.
The WrapPanel acts much like a StackPanel except that when the items stack to the edge of the panel they wrap. The same caveats with scroll bars apply, in many cases you have to set a height or width to get it to wrap items properly (since the height and width properties are basically evil try using MaxHeight/Width).