如何从 WP7 的列表选择器中读取所选项目？

Question

我的 XAML 中有以下列表选择器；

<toolkit:ListPicker Name="CategoryPicker" ItemsSource="{Binding Category}" CacheMode="BitmapCache" FullModeHeader="{Binding Path=Resources.TheHeader}" SelectedIndex="{Binding TheCurrentIndex, Mode=OneWay}" IsEnabled="{Binding IsViewEnabled}" TabIndex="0" Margin="12,229,12,-205" SelectionChanged="CategoryPicker_SelectionChanged">
<toolkit:ListPicker.ItemTemplate>
    <DataTemplate>
        <StackPanel Orientation="Horizontal" HorizontalAlignment="Center">
            <TextBlock Text="{Binding CategoryDesc}" FontFamily="{StaticResource PhoneFontFamilySemiBold}" FontSize="{StaticResource PhoneFontSizeMediumLarge}" />
        </StackPanel>
    </DataTemplate>
</toolkit:ListPicker.ItemTemplate>
<toolkit:ListPicker.FullModeItemTemplate>
    <DataTemplate>
        <StackPanel x:Name="item" Orientation="Horizontal" Margin="5, 24, 0, 24">
            <TextBlock Margin="15, 0, 0, 0" Text="{Binding CategoryDesc}" FontSize="40" TextWrapping="Wrap" />
        </StackPanel>
    </DataTemplate>
</toolkit:ListPicker.FullModeItemTemplate>

我已经能够通过 LINQ 从 SQL CE 数据表中填充列表选择器，但我正在努力检索所选项目的值。

我尝试了以下方法；

ListPickerItem selectedItem = CategoryPicker.ItemContainerGenerator.ContainerFromItem(this.CategoryPicker.SelectedItem) as ListPickerItem;

我认为我没有正确理解这一点，但我似乎无法阅读所选项目的文本值，一如既往地感谢所有帮助！

编辑

类别的原始表定义如下；

[Table(Name = "Categories")]
    public class Categories : INotifyPropertyChanged, INotifyPropertyChanging
    {
        // Define ID: private field, public property and database column.
        private int _categoryId;

        [Column(IsPrimaryKey = true, IsDbGenerated = true, DbType = "INT NOT NULL Identity", CanBeNull = false, AutoSync = AutoSync.OnInsert)]
        public int CategoryId
        {
            get
            {
                return _categoryId;
            }
            set
            {
                if (_categoryId != value)
                {
                    NotifyPropertyChanging("CategoryId");
                    _categoryId = value;
                    NotifyPropertyChanged("CategoryId");
                }
            }
        }

        // Define item category: private field, public property and database column.
        private string _categoryDesc;

        [Column]
        public string CategoryDesc
        {
            get
            {
                return _categoryDesc;
            }
            set
            {
                if (_categoryDesc != value)
                {
                    NotifyPropertyChanging("CategoryDesc");
                    _categoryDesc = value;
                    NotifyPropertyChanged("CategoryDesc");
                }
            }
        }
        #region INotifyPropertyChanged Members

        public event PropertyChangedEventHandler PropertyChanged;

        // Used to notify the page that a data context property changed
        private void NotifyPropertyChanged(string propertyName)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
            }
        }

        #endregion

        #region INotifyPropertyChanging Members

        public event PropertyChangingEventHandler PropertyChanging;

        // Used to notify the data context that a data context property is about to change
        private void NotifyPropertyChanging(string propertyName)
        {
            if (PropertyChanging != null)
            {
                PropertyChanging(this, new PropertyChangingEventArgs(propertyName));
            }
        }

        #endregion
    }

Category 的属性是；

private ObservableCollection<DBControl.Categories> _category;
public ObservableCollection<DBControl.Categories> Category
    {
        get
        {
            return _category;
        }
        set
        {
            if (_category != value)
            {
                _category = value;
                NotifyPropertyChanged("Category");
            }
        }
    }

希望这会有所帮助。

Answer 1

看起来您访问 SelectedItem 的方式不正确。基本上，当您在 WP7 中使用 SQL CE 并将从数据库收到的结果绑定到数据控件时，它正在存储该特定类型的对象。

在这种情况下，假设您从数据库中收到的项目是 Category 类型，并且您将其绑定到 ListPicker。当有人选择一个项目时，您只需像这样访问它：

Categories selectedCategory = CategoryPicker.SelectedItem as Categories;