WPF PRISM 6 DelegateComand ObservesCanExecute - wpf

Question

Thanks in advance!
How should I use ObservesCanExecute in the DelegateCommand of PRISM 6?
public partial class UserAccountsViewModel: INotifyPropertyChanged
{
public DelegateCommand InsertCommand { get; private set; }
public DelegateCommand UpdateCommand { get; private set; }
public DelegateCommand DeleteCommand { get; private set; }
public UserAccount SelectedUserAccount
{
get;
set
{
//notify property changed stuff
}
}
public UserAccountsViewModel()
{
InitCommands();
}
private void InitCommands()
{
InsertCommand = new DelegateCommand(Insert, CanInsert);
UpdateCommand = new DelegateCommand(Update,CanUpdate).ObservesCanExecute(); // ???
DeleteCommand = new DelegateCommand(Delete,CanDelete);
}
//----------------------------------------------------------
private void Update()
{
//...
}
private bool CanUpdate()
{
return SelectedUserAccount != null;
}
//.....
}
Unfortunatelly, I'm not familiar with expressions in c#. Also, I thought this would be helpful to others.

Answer 1

ObservesCanExecute() works “mostly like” the canExecuteMethod parameter of DelegateCommand(Action executeMethod, Func<bool> canExecuteMethod).
However, if you have a boolean property instead of a method, you don't need to define a canExecuteMethod with ObservesCanExecute.
In your example, suppose that CanUpdate is not a method, just suppose that it's a boolean property.
Then you can change the code to ObservesCanExecute(() => CanUpdate) and the DelegateCommand will execute only if the CanUpdate boolean property evaluates to true (no need to define a method).
ObservesCanExecute is like a “shortcut” over a property instead of having to define a method and having passing it to the canExecuteMethod parameter of the DelegateCommand constructor.