c# - 无法使用从 MSDN 复制的代码覆盖继承的成员 SelectTemplate...

Question

我有一个覆盖问题。我知道你不能覆盖继承的成员，除非它们被标记为虚拟、抽象或覆盖，但是......

我有 这个来自 msdn 的代码：

using System.Windows;
using System.Windows.Controls;

namespace SDKSample
{
    public class TaskListDataTemplateSelector : DataTemplateSelector
    {
        public override DataTemplate
            SelectTemplate(object item, DependencyObject container)
        {
            FrameworkElement element = container as FrameworkElement;

            if (element != null && item != null && item is Task)
            {
                Task taskitem = item as Task;

                if (taskitem.Priority == 1)
                    return
                        element.FindResource("importantTaskTemplate") as DataTemplate;
                else 
                    return
                        element.FindResource("myTaskTemplate") as DataTemplate;
            }

            return null;
        }
    }
}

我添加了这段代码：

public class PostTemplateSelector : DataTemplateSelector
{
    public override DataTemplate SelectTemplate(object item, DependencyObject container)
    {
        ListViewItem lvi = item as ListViewItem;

        AppNetClient.PostClass key = lvi.DataContext as AppNetClient.PostClass;

        if (key.postTemplate == "Post")
        {
            return lvi.FindName("PostDataTemplate") as DataTemplate;
        }
        else
        {
            return lvi.FindName("SelectedPostDataTemplate") as DataTemplate;
        }
    }
}

我得到这个错误：

Error   3   'oneSocialLife.MainPage.PostTemplateSelector.SelectTemplate(object, Windows.UI.Xaml.DependencyObject)': cannot override inherited member 'Windows.UI.Xaml.Controls.DataTemplateSelector.SelectTemplate(object, Windows.UI.Xaml.DependencyObject)' because it is not marked virtual, abstract, or override   C:\Users\kcone\documents\visual studio 2012\Projects\HttpClientApp\HttpClientApp\MainPage.xaml.cs   339 42  oneSocialLife

我花了几个小时寻找原因，但无法弄清楚。有任何想法吗？

Answer 1

您引用的示例适用于 WPF ( System.Windows.Controls.DataTemplateSelector )。

在 Windows 应用商店应用程序中，您使用的是具有不同语义的Windows.UI.Xaml.Controls.DataTemplateSelector，并且SelectTemplate确实不可覆盖，但SelectTemplateCore是。

Answer 2

最终工作的代码：来自：http: //msdn.microsoft.com/en-us/library/ms742521.aspx 也：http ://www.switchonthecode.com/tutorials/wpf-tutorial-how-to-使用数据模板选择器

public class PostTemplateSelector : DataTemplateSelector
{
    public DataTemplate PostTemplate { get; set; }
    public DataTemplate SelectedPostTemplate { get; set; }

    protected override DataTemplate SelectTemplateCore(object item, DependencyObject container)
    {
        //ListViewItem lvi = item as ListViewItem;
        //AppNetClient.PostClass key = lvi.DataContext as AppNetClient.PostClass;

        AppNetClient.PostClass key = item as AppNetClient.PostClass;

        if (key.postTemplate == "Post")
        {
            return PostTemplate;
        }
        else
        {
            return SelectedPostTemplate;
        }
    }
}