ListPicker IndexOutOfRangeException

Question

我的ListPicker控件有问题。我在我的页面中实现了我的列表选择器，如下所示，但我在运行时收到了一个IndexOutOfRangeException，我不太确定如何解决这个问题：

SettingsPage.xaml

<phone:PhoneApplicationPage.Resources>
    <DataTemplate x:Name="SearchProviderItemTemplate">
        <TextBlock Text="{Binding SearchProvider}" />
    </DataTemplate>
</phone:PhoneApplicationPage.Resources>

<ScrollViewer x:Name="ContentPanel_Browser" Margin="12,0,12,0">
                <Grid>
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition/>
                        <ColumnDefinition/>
                    </Grid.ColumnDefinitions>
                    <Grid.RowDefinitions>
                        <RowDefinition Height="Auto"/>
                        <RowDefinition Height="70"/>
                        <RowDefinition Height="70"/>
                        <RowDefinition/>
                        <RowDefinition/>
                        <RowDefinition/>
                    </Grid.RowDefinitions>

                    ...

                    <!-- Search Provider -->
                    <TextBlock Text="Search provider" Margin="12,7,12,8"
                       Grid.Row="3" VerticalAlignment="Bottom"
                       Foreground="{StaticResource PhoneSubtleBrush}"/>
                    <toolkit:ListPicker x:Name="SearchProviderListPicker" Grid.Row="4" Grid.ColumnSpan="2" Margin="12,0,12,0"  
                                        ItemTemplate="{Binding SearchProviderItemTemplate}" 
                                        SelectionChanged="SearchProviderListPicker_SelectionChanged" />
                </Grid>
            </ScrollViewer>                

SettingsPage.xaml.cs

    string searchProvider;

    String[] SearchProvider = 
    {
        "Google", 
        "Bing",
        "Yahoo",
        "Ask",
        "AOL"
    };

    private void SearchProviderListPicker_SelectionChanged(object sender, SelectionChangedEventArgs e)
    {
        string selectedItem = e.AddedItems[0] as string;  //IndexOutOfRangeException was unhandled

        switch (selectedItem)
        {
            case "Google":
                searchProvider = "http://www.google.com/search?q=";
                break;
            case "Bing":
                searchProvider = "http://www.bing.com/search?q=";
                break;
            case "Yahoo":
                searchProvider = "http://search.yahoo.com/search?p=";
                break;
            case "Ask":
                searchProvider = "http://www.ask.com/web?q=";
                break;
            case "AOL":
                searchProvider = "http://search.aol.com/search?q=";
                break;
            //default:
            //    SearchProvider = "http://search.aol.com/search?q=";
            //    break;
        }

字符串在SettingsPage.xaml.cs中以行'string selectedItem = e.AddedItems as string;‘出现。我记得我在StackOverflow上看到了如何解决这个问题，但我现在找不到那个源代码。关于如何设置界限或检查以确保此异常不会发生，您有什么想法吗？提前感谢(任何代码帮助都会对我有帮助！)

Answer 1

因为AddedItems是一个IList，你能不能在尝试访问它们之前检查一下它里面有没有一些项目？

在该方法的顶部类似于以下内容应该可以解决这个问题：

if (e.AddedItems.Count <= 0)
{
    return;
}