Question

I’m using a MVVM pattern with Prism

I’ve got a list of Elements in an ObservableCollection, in my Model. In my View, i binded the ObservableCollection to a Listview, then i trye to display 1 button that is binded to a DelegateCommand called DoSomethingCommand. That means that each line of my Listview have a button to call DoSomethingCommand, with a CommandParameter binded to the ID of the element.

Constraint: DoSomethingCommand will change the status field of my element to “done”. When an element is “done” i want the button to call DoSomethingCommand to be disabled.

So logically, all i have to do is have a canExecuteDoSomethingCommand delegate when i implement the command. But, the problem is when and how can i raise DoSomethingCommand.RaiseCanExecuteChanged?
BTW Element is part of a third party dll that i can’t modify it, but it already implements INotifyPropertyChanged.

<ListView BorderThickness="0" Width="Auto"
              ItemsSource="{Binding ElementList}"
              >
   <ListView.View>
     <GridView>
       <GridViewColumn Header="Actions">
         <GridViewColumn.CellTemplate>
             <DataTemplate>
                <StackPanel Orientation="Horizontal">
                     <Button Command="{Binding DataContext.DoSomethingCommand, RelativeSource={RelativeSource AncestorType={x:Type ListView}}}" CommandParameter="{Binding ID}" >Accept</Button>
                </StackPanel>
             </DataTemplate>
           </GridViewColumn.CellTemplate>
        </GridViewColumn>

Implemting the command

DoSomethingCommand = new DelegateCommand<string>(executeDoSomethingCommand, canExecuteDoSomethingCommand);

Answer 1

If you are using Prism’s EventAggregator, and I assume that you are since you’re using Prism, then you can subscribe to an event and call RaiseCanExecuteChanged() on your DelegateCommand.

Something like this:

_eventAggregator.GetEvent<YourCompositePresentationEvent>().Subscribe((i) => { YourDelegateCommand.RaiseCanExecuteChanged(); });