Today I’d like to share a trick I used while developing my first Windows Store application. I’m very new to this technology and it’s my first article about it, so I hope I won’t make a fool of myself… It’s often useful to be notified when the value of a dependency property changes; many controls expose events for that purpose, but it’s not always the case. For instance, recently I was trying to detect when the Content property of a ContentControl changed.
The DataContext property in WPF is extremely handy, because it is automatically inherited by all children of the element where you assign it; therefore you don't need to set it again on each element you want to bind. However, in some cases the DataContext is not accessible: it happens for elements that are not part of the visual or logical tree. It can be very difficult then to bind a property on those elements… Let's illustrate with a simple example: we want to display a list of products in a DataGrid.
THE feature that was missing from WPF ! Visual Studio 2010 beta 2 has been released last week, and it brings to WPF a long awaited feature : support for bindings in InputBindings. As a reminder, the issue in previous releases was that the Command property of the InputBinding class wasn't a DependencyProperty, so it wasn't possible to bind it. Furthermore, InputBindings didn't inherit the parent DataContext, which made it difficult to provide alternative implementations… Until now, in order to bind the Command of a KeyBinding or MouseBinding to a property of the DataContext, we had to resort to clumsy workarounds… I had eventually came up with an acceptable solution, described in this post, but I wasn't really satisfied with it (it used reflection on private members, and had annoying limitations).
As you may have noticed, it is not possible to modify the contents of an ObservableCollection on a separate thread if a view is bound to this collection : the CollectionView raises a NotSupportedException : This type of CollectionView does not support changes to its SourceCollection from a thread different from the Dispatcher thread To illustrate this, let's take a simple example : a ListBox bound to a collection of strings in the ViewModel :
Hi, this is my first post on this blog, I hope you will enjoy it ;-). If you want to know a few things about me, please check out this page. The end-user of any application expects that his preferences (window size, state of this or that option…) are saved to be restored at the next run : that's why .NET 2.0 introduced application settings as a unified way to persist these settings.