Question

我有覆盖问题。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......

我有来自msdn的this code：

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;
        }
    }
}

我收到了这个错误：

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，但无法弄明白。有什么想法吗？

Answer 1

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

在Windows应用商店应用中，您使用的Windows.UI.Xaml.Controls.DataTemplateSelector具有不同的语义，而SelectTemplate确实无法覆盖，但SelectTemplateCore是。

Answer 2

最终工作的代码：来自：http://msdn.microsoft.com/en-us/library/ms742521.aspx 还有：http://www.switchonthecode.com/tutorials/wpf-tutorial-how-to-use-a-datatemplateselector

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;
        }
    }
}

无法覆盖继承的成员SelectTemplate ...使用从MSDN复制的代码

2 个答案: