Cancel combobox selection in WPF with MVVM

Question

I\'ve got a combobox in my WPF application:

Answer 1

--Xaml

--ViewModel

private object _SelectedItem;
public object SelectedItem 
{
    get { return _SelectedItem;}
    set {
           if(_SelectedItem == value)// avoid rechecking cause prompt msg
            { 
               return;
            } 
            MessageBoxResult result = MessageBox.Show
                    ("Continue change?", MessageBoxButton.YesNo);
            if (result == MessageBoxResult.No)
            {
                ComboBox combo = (ComboBox)sender;
                handleSelection = false;
                combo.SelectedItem = e.RemovedItems[0];
                return;
            }
            _SelectedItem = value;
            RaisePropertyChanged(); 
        }
}