WPF Update button state from inside command - wpf

Question

Having different buttons on a view, how could I control the IsEnabled state of the buttons when a command is being executed?
If I execute this command:
public ICommand DoSomethingCommand
{
get
{
if (doSomethingCommand == null)
{
doSomethingCommand = new RelayCommand(
(parameter) =>
{
this.IsBusy = true;
this.someService.DoSomething(
(b, m) =>
{
this.IsBusy = false;
}
);
},
(parameter) => !this.IsBusy);
}
return this.doSomethingCommand ;
}
}
I set the IsBusy property which fires the OnPropertyChanged event. All the other buttons check this property in their command's CanExecute. But the buttons do not get disabled, when the above command is executed.
How do I do this right?

Answer 1

CanExecuteChanged needs to fire in order for the Command Source to know to invoke CanExecute.
A simple way to do this is to invoke CommandManager.InvalidateRequerySuggested().
bool _isBusy;
public bool IsBusy
{
get { return _isBusy; }
set
{
if (value == _isBusy)
return;
_isBusy = value;
//NotifyPropertyChanged("IsBusy"); // uncomment if IsBusy is also a Dependency Property
System.Windows.Input.CommandManager.InvalidateRequerySuggested();
}
}

Answer 2

why not implement INotifyPropertyChanged on your own custom version of the RelayCommand class. This will conform to MVVM:
public class RelayCommand : ICommand, INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
private readonly Action execute;
private readonly Func<bool> canExecute;
private bool isBusy;
public bool IsBusy
{
get { return isBusy; }
set
{
isBusy = value;
var handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs("IsBusy"));
}
}
}
public event EventHandler CanExecuteChanged
{
add
{
if (this.canExecute != null)
{
CommandManager.RequerySuggested += value;
}
}
remove
{
if (this.canExecute != null)
{
CommandManager.RequerySuggested -= value;
}
}
}
public RelayCommand(Action execute) : this(execute, null)
{
}
public RelayCommand(Action execute, Func<bool> canExecute)
{
if (execute == null)
{
throw new ArgumentNullException("execute");
}
this.execute = execute;
this.canExecute = canExecute;
}
public void Execute(object parameter)
{
this.IsBusy = true;
this.execute();
this.IsBusy = false;
}
public bool CanExecute(object parameter)
{
return this.canExecute == null ? true : this.canExecute();
}
}
then use the command like this:
<Button Command="{Binding Path=DoSomethingCommand}"
IsEnabled="{Binding Path=DoSomethingcommand.IsBusy,
Converter={StaticResource reverseBoolConverter}}"
Content="Do It" />