WPF Application developers would be experiencing or would have observed that after updating MVVMLight Toolkit package to Version 5.0.0 or 5.0.1, RelayCommand - CanExecute() mechanism is not working anymore. This issue is been already reported by MVVMLight user on codeplex as Issue# 7659. As explained by Laurent: WPF is the only XAML framework that uses the CommandManager to automagically raise the CanExecuteChanged event on ICommands. Unfortunately, there is no CommandManager in PCL (po » Read more