WP8 ListPicker SelectionChanged在开始时触发

Question

I have a ListPicker with a SelectionChanged Event. I want the SelectionChange event to only fire when I change the selection, obviously, but in my case, it is also firing whenever I load the page.

Code:

<toolkit:ListPicker x:Name="sightingTypesPicker" ItemsSource="{Binding sightingTypes, ElementName=this}" SelectionChanged="sightingTypesPicker_SelectionChanged">
   <toolkit:ListPicker.ItemTemplate>
      <DataTemplate>
         <StackPanel>
            <TextBlock Text="{Binding Name}" FontSize="{StaticResource PhoneFontSizeSmall}"/>
         </StackPanel>
      </DataTemplate>
   </toolkit:ListPicker.ItemTemplate>
   <toolkit:ListPicker.FullModeItemTemplate>
      <DataTemplate>
         <StackPanel>
            <TextBlock Text="{Binding Name}" FontSize="{StaticResource PhoneFontSizeLarge}"/>
            <TextBlock Visibility="Collapsed" Text="{Binding TypeId}" FontSize="{StaticResource PhoneFontSizeSmall}"/>
         </StackPanel>
      </DataTemplate>
   </toolkit:ListPicker.FullModeItemTemplate>
</toolkit:ListPicker>

C#:

private void sightingTypesPicker_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
    SightingType selecteditem = e.AddedItems[0] as SightingType;
    Sighting.Instance.TypeId = selecteditem.TypeID;
}

Answer 1

基本上，通过默认，列表选择器或列表框或组合框或任何下拉列表具有特定的选定项目，即列表框的第零个项目。/..等。因此，在加载页面并将数据填充到列表框，否则将触发从-1的选择更改，即无数据状态到0选择更改为默认值:)

Answer 2

You can add the handler on the Loaded event handler in your code so you ensure it's only called after that.

Update:

For example add this code in Loaded event of your page instead of XAML:

sightingTypesPicker.SelectionChanged += sightingTypesPicker_SelectionChanged;