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在我的代码中，

    protected override void OnNavigatedTo(NavigationEventArgs e)
    {
        using (bus_noContext ctx = new bus_noContext(bus_noContext.ConnectionString))
        {
            ctx.CreateIfNotExists();
            ctx.LogDebug = true;
            var buses = from c in ctx.Bus_routes
                             select new bus_list{ BUS_NO = c.BUS_NO, SOURCE = c.SOURCE, DESTINATION = c.DESTINATION};
            busno_list.ItemsSource = buses.ToList();
        }
    }

    private void TextBox_TextChanged(object sender, TextChangedEventArgs e)
    {
        string temp;
        TextBlock nameBox;
        ListBoxItem currentSelectedListBoxItem;
        for(int i=0;i<busno_list.Items.Count;i++)
        {
            currentSelectedListBoxItem = this.busno_list.ItemContainerGenerator.ContainerFromIndex(i) as ListBoxItem;

            nameBox = FindDescendant<TextBlock>(currentSelectedListBoxItem);

            temp = nameBox.Text;
            if (temp.Contains(searchbox.Text))
            {
                busno_list.SelectedIndex = i;
                busno_list.ScrollIntoView(busno_list.SelectedItem);
                return;
            }
        }
    }

在 FindDescendant 函数中，

    private T FindDescendant<T>(DependencyObject obj) where T : DependencyObject
    {
        // Check if this object is the specified type
        if (obj is T)
            return obj as T;

        // Check for children
        int childrenCount = VisualTreeHelper.GetChildrenCount(obj);
        if (childrenCount < 1)
            return null;

        // First check all the children
        for (int i = 0; i < childrenCount; i++)
        {
            DependencyObject child = VisualTreeHelper.GetChild(obj, i);
            if (child is T)
                return child as T;
        }

        // Then check the childrens children
        for (int i = 0; i < childrenCount; i++)
        {
            DependencyObject child = FindDescendant<T>(VisualTreeHelper.GetChild(obj, i));
            if (child != null && child is T)
                return child as T;
        }

        return null;
    }

但是在
int childrenCount = VisualTreeHelper.GetChildrenCount(obj);
调试器总是抛出 InvalidOperationException（引用不是有效的可视 DependencyObject），并且在 Autos 监视工具中，obj 显示空值，即使列表框中已经有 557 行。

所以我无法纠正这个异常。
我发现这种方法最适合搜索具有数据模板的列表框，如如何使用 DataTemplate 访问列表框中的特定项目？. 请建议我哪里出错了，或者是否有更好的选择。

4

1 回答 1

1

不知道为什么你试图通过找到生成的元素来做到这一点，当你有源时，比如：

protected override void OnNavigatedTo(NavigationEventArgs e)
{
    using (bus_noContext ctx = new bus_noContext(bus_noContext.ConnectionString))
    {
        ctx.CreateIfNotExists();
        ctx.LogDebug = true;
        var buses = from c in ctx.Bus_routes
                         select new bus_list{ BUS_NO = c.BUS_NO, SOURCE = c.SOURCE, DESTINATION = c.DESTINATION};
        busno_list.ItemsSource = buses.ToList();

        searchbox.Text = buses[20].SOURCE; // or whatever
    }
}
于 2013-09-08T20:17:22.717 回答