WPF 如何从 DataTemplate 访问控件

我有一个包含网格的数据模板，网格内有一个组合框。

<DataTemplate x:Key="ShowAsExpanded">
        <Grid>                
            <ComboBox Name ="myCombo" Grid.Column="1" HorizontalAlignment="Stretch" VerticalAlignment="Top" Margin="5"
                      IsSynchronizedWithCurrentItem="True"
                      ItemsSource="{Binding}"
                      ItemTemplate="{StaticResource MyItems}">
                <ComboBox.ItemsPanel>
                    <ItemsPanelTemplate>
                        <VirtualizingStackPanel />
                    </ItemsPanelTemplate>
                </ComboBox.ItemsPanel>
            </ComboBox>

        </Grid>
    </DataTemplate>

然后我有一个通过样式引用该模板的网格。

<Grid>
    <ContentPresenter Name="_contentPresenter" Style="{DynamicResource StyleWithCollapse}" Content="{Binding}" />
</Grid>

如何通过 Combo 背后的代码访问以基本设置其 DataContext？

我所知道的三种方式。

1.使用查找名称

ComboBox myCombo =
    _contentPresenter.ContentTemplate.FindName("myCombo",
                                               _contentPresenter) as ComboBox;

2.将 Loaded 事件添加到 ComboBox 并从那里访问它

<ComboBox Name ="myCombo" Loaded="myCombo_Loaded" ...

private void myCombo_Loaded(object sender, RoutedEventArgs e)
{
    ComboBox myCombo = sender as ComboBox; 
    // Do things..
}

3.在视觉树中找到它

private void SomeMethod()
{
    ComboBox myCombo = GetVisualChild<ComboBox>(_contentPresenter);
}
private T GetVisualChild<T>(DependencyObject parent) where T : Visual
{
    T child = default(T);
    int numVisuals = VisualTreeHelper.GetChildrenCount(parent);
    for (int i = 0; i < numVisuals; i++)
    {
        Visual v = (Visual)VisualTreeHelper.GetChild(parent, i);
        child = v as T;
        if (child == null)
        {
            child = GetVisualChild<T>(v);
        }
        if (child != null)
        {
            break;
        }
    }
    return child;
}