c# - 在 ComboBox DataTemplate 中获取 TextBlock 的值

Question

我有以下 XAML:

<ComboBox Height="23" HorizontalAlignment="Left" Grid.Row="6" Grid.Column="2"
          Name="cbo_team" VerticalAlignment="Top" Width="148"
          DataContext="{Binding ElementName=cbo_component, Path=SelectedItem}"
          SelectedIndex="0">
    <ComboBox.ItemsSource>
        <Binding XPath="Teams/Team/@id"
                 Converter="{StaticResource xmlConverter}">
            <Binding.ConverterParameter>
                <local:XmlConverterParameter
                    XPathTemplate="/Products/Teams/Team[{0}]"
                    XPathCondition="@id='{0}'" />
            </Binding.ConverterParameter>
        </Binding>
    </ComboBox.ItemsSource>
    <ComboBox.ItemTemplate>
        <DataTemplate>
            <TextBlock Text="{Binding XPath=@name}" />
        </DataTemplate>
    </ComboBox.ItemTemplate>
</ComboBox>

在 C# 中，我试图获取 ComboBox 中当前所选项目中的 TextBlock 的值。我怎么做？ This question几乎相同，但唯一的答案无济于事。

Answer 1

检查此示例。文本 block (组合框下方)显示组合框中当前选定的 xml 元素的名称属性的值。将弹出一个消息框，其中包含在可视化树中查找的相同结果。初始选择更改时查找失败。看起来组合框项目是在设置所选项目后创建的。

XAML:

<Window x:Class="CBTest.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Height="300" Width="300">

    <Window.Resources>
        <XmlDataProvider x:Key="UsersData" XPath="Users">
            <x:XData>
                <Users xmlns="">
                    <User name="Sally" />
                    <User name="Lucy" />
                    <User name="Linus" />
                    <User name="Charlie" />
                </Users>
            </x:XData>
        </XmlDataProvider>
    </Window.Resources>

    <StackPanel>

        <ComboBox 
            Name="_comboBox"
            ItemsSource="{Binding Source={StaticResource UsersData},XPath=*}"
            SelectedIndex="0"
            SelectionChanged="OnComboBoxSelectionChanged">
            <ComboBox.ItemTemplate>
                <DataTemplate>
                    <TextBlock Text="{Binding XPath=@name}" Name="nameTextBlock" />
                </DataTemplate>
            </ComboBox.ItemTemplate>
        </ComboBox>

        <!-- Below shows how to get the value of selected item directly from the data. -->
        <TextBlock 
            DataContext="{Binding Path=SelectedItem, ElementName=_comboBox}"
            Text="{Binding XPath=@name}" />

    </StackPanel>

</Window>

后面的代码，展示了如何通过遍历可视化树直接获取文本:

private void OnComboBoxSelectionChanged(object sender, SelectionChangedEventArgs e)
{
    ComboBox comboBox = sender as ComboBox;
    ComboBoxItem comboBoxItem = comboBox.ItemContainerGenerator.ContainerFromItem(comboBox.SelectedItem) as ComboBoxItem;
    if (comboBoxItem == null)
    {
        return;
    }
    TextBlock textBlock = FindVisualChildByName<TextBlock>(comboBoxItem, "nameTextBlock");
    MessageBox.Show(textBlock.Text);
}

private static T FindVisualChildByName<T>(DependencyObject parent, string name) where T : DependencyObject
{
    for (int i = 0; i < VisualTreeHelper.GetChildrenCount(parent); i++)
    {
        var child = VisualTreeHelper.GetChild(parent, i);
        string controlName = child.GetValue(NameProperty) as string;
        if (controlName == name)
        {
            return child as T;
        }
        T result = FindVisualChildByName<T>(child, name);
        if (result != null)
            return result;
    }
    return null;
}