How can I extend a ComboBox to support commands (MVVM)?

Question

Hi, As topic says, I need to extend the features of a standard Silverlight ComboBox to also support Commanding. Since I follow MVVM I need my ComboBox to communicate the SelectionChanged event to my ViewModel.

What would the code look like for doing this? I want to be able to put the Command attribute on my ComboBox XAML control.

Using (WCF RIA, MVVM, VB.NET)..

All tips appricated!

Answer 1

Create a behavior that exposes an ICommand Command and a object CommandParameter. In the behavior wire up to the SelectionChanged event of your AssociatedObject. Then you can bind the command to your behavior and simulate a command for the SelectionChanged event.

Answer 2

You can bind the property SelectedIndex or SelectedItem of the Combobox to your ViewModel. So you don´t need any Commands.

XAML

<ComboBox SelectedIndex="{Binding SelectedIndex, Mode=TwoWay}"/>

C#

public class ViewModel
{
   private int _selectedIndex;
   public int SelectedIndex {
     get { return _selectedIndex; }
     set { 
       if (value != _selectedIndex) {
         _selectedIndex = value;
         // Perform any logic, when the SelectedIndex changes.
       }
     } 
   }
}