What is the easiest way to handle SelectedItem event with MVVM?

Question

In the code below, when user selects Customer in the combobox, the customer\'s name is displayed in a textbox. I fill the Combox box with an O

Answer 1

You should be able to bind a property in you ViewModel to the SelectedItem property of the combobox. If you set this up as two way binding you will be notified when the SelectedItem is changed because it will trigger the set method on the property.

ViewModel:

public ObservableCollection Customers
{
   get { return _customers; }
   set
   {
       if (_customers != value)
       {
           _customers = value;
           OnPropertyChanged("Customers");
       }
   }
}

public Customer SelectedCustomer
{
   get { return _selectedCustomer; }
   set
   {
       if (_selectedCustomer != value)
       {
           _selectedCustomer= value;
           LastName= value.LastName;
           OnPropertyChanged("SelectedCustomer");
       }
   }
}

public Customer LastName
{
   get { return _lastName; }
   set
   {
       if (_lastName!= value)
       {
           _lastName= value;
           OnPropertyChanged("LastName");
       }
   }
}

Xaml:

<DockPanel LastChildFill="False" Margin="10">
    <ComboBox 
        x:Name="CustomerList"
        ItemTemplate="{StaticResource CustomerTemplate}"
        HorizontalAlignment="Left"
        DockPanel.Dock="Top" 
        Width="200"
        SelectedItem="{Binding SelectedCustomer, Mode=TwoWay}"
        ItemsSource="{Binding Customers}"/>

    <TextBlock x:Name="CurrentlySelectedCustomer"
               Text="{Binding LastName}"/>
</DockPanel>

Answer 2

Have a look at this application on www.codeproject.com. Here I use the CollectionView to detect the currently selected item

Update

Using CollectionView to detect current selected item

ListCollectionView view = (ListCollectionView)CollectionViewSource.GetDefaultView(Customers); 
view.CurrentChanged += delegate 
{ 
    SelectedCustomer= (Customer)view.CurrentItem; 
};

Just remember to also set IsSynchronizedWithCurrentItem="True"