在MVVM中绑定ListPicker（Selection_Changed）

Question

I am trying to attach a command to the event Selection_Changed of the ListPicker

I have the following code for the listpicker in my xaml :

   <toolkit:ListPicker 
         x:name="picker" ItemsSource="{Binding Sentences}"    
         SelectionChanged="{Binding PickerCommand, Mode=TwoWay}" >
            <toolkit:ListPicker.ItemTemplate>
                <DataTemplate>
                    <TextBlock Text="{Binding }"/>
                </DataTemplate>
            </toolkit:ListPicker.ItemTemplate>
        </toolkit:ListPicker>

Sentences is just a list of string in my ViewModel, how can I create a simple Commad for example that will just show a MessageBox with the current selected string in the ListPicker ?

Something similar to this function that i wrote in the code Behind :

private void PickerCommand(object sender, SelectionChangedEventArgs e)
{
    if (piker.SelectedItem != null) 
    {
      MessageBox.Show(piker.SelectedItem.ToString());
    }
}

EDIT :

I just created this simple function :

public void Test()
{
MessageBox.Show("Test!");
}

passed it :

PickerCommand = new RelayCommand<SelectionChangedEventArgs>(Test);

But I have the error saying that the argument that I passed is invalid, why is that ?

Answer 1

You need to do this:

<toolkit:ListPicker x:name="picker" ItemsSource="{Binding Sentences}">
 <i:Interaction.Triggers>
    <i:EventTrigger EventName="SelectionChanged">
        <command:EventToCommand Command="{Binding PickerCommand, Mode=OneWay}" />
    </i:EventTrigger>
</i:Interaction.Triggers>
        <toolkit:ListPicker.ItemTemplate>
            <DataTemplate>
                <TextBlock Text="{Binding }"/>
            </DataTemplate>
        </toolkit:ListPicker.ItemTemplate>

and then

    public class MYViewModel :ViewModelBase
{
   public MyViewModel()
   {
       PickerCommand = new RelayCommand<object>(ActionForPickerCommand);
    }
    public ICommand PickerCommand {get;set;}
}

Use MVVM Light, that has some classes that help in it.