Read original post by Diederik Krols at U2U Blog
This article describes two behaviors of the native XAML Slider control that reduce the joy of using it in MVVM Windows 8 Store apps. We all agree that XAML is one of the nicest technologies to develop Windows 8 Store apps, right? We all agree that you should use MVVM to build XAML apps, right? No, we don’t: unfortunately some of the native controls strongly disagree with us. The most well-known example of an MVVM-unfriendly XAML control is the radio button. A radio button is cleared by selecting another radio button in the same group. That’s OK, but at that moment it also clears its binding. It breaks the link to the viewmodels to which it was bound. This classic MVVM problem is generally solved by assigning a unique GroupName to each radio button, and deal with the mutual exclusiveness programmatically on the viewmodels’ side. Ouch!