Question

基于MSDN的这个例子，我创建了一个“非通用自定义集合类，它派生自ObservableCollection，并将其约束为特定类型。”这用作listview控件的ItemsSource属性。这一切都很完美，xaml设计视图显示我加载到自定义集合类中的示例数据。

当我尝试构建项目时会出现问题;我收到此错误：“错误1 XML命名空间中的未知类型'ThreadCollection'clr-namespace：Messaging_2._0; assembly = Messaging 2.0.WindowsPhone，Version = 1.0.0.0，Culture = neutral，PublicKeyToken = null'C：\ Users \ Wesley \ Source \ Repos \ Messenging 2.0 \ Messaging 2.0 \ Messaging 2.0 \ Messaging 2.0.WindowsPhone \ MainPage.xaml 14 10 Messaging 2.0.WindowsPhone。

此错误源自以下xaml代码的行<c:ThreadCollection x:Key="MainThreadCollection"/>。

<Page
x:Class="Messaging_2._0.MainPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:Messaging_2._0"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:c="clr-namespace:Messaging_2._0"

mc:Ignorable="d"
Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">

<Page.Resources>
    <c:ThreadCollection x:Key="MainThreadCollection"/>
</Page.Resources>
<The code for the listview control is here, I haven't included it because it works as I expect.>

以下是xaml引用的C＃代码：

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices.WindowsRuntime;
using Windows.Foundation;
using Windows.Foundation.Collections;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Controls.Primitives;
using Windows.UI.Xaml.Data;
using Windows.UI.Xaml.Input;
using Windows.UI.Xaml.Media;
using Windows.UI.Xaml.Navigation;
using System.Collections.ObjectModel;

// The Blank Page item template is documented at http://go.microsoft.com/fwlink/?LinkId=234238

namespace Messaging_2._0
{
    /// <summary>
    /// An empty page that can be used on its own or navigated to within a Frame.
    /// </summary>
    public sealed partial class MainPage : Page
    {
        public ThreadCollection MainThreadCollection = new ThreadCollection();

        public MainPage()
        {
            this.InitializeComponent();

            this.NavigationCacheMode = NavigationCacheMode.Required;
            this.DataContext = this;
        }

        /// <summary>
        /// Invoked when this page is about to be displayed in a Frame.
        /// </summary>
        /// <param name="e">Event data that describes how this page was reached.
        /// This parameter is typically used to configure the page.</param>
        protected override void OnNavigatedTo(NavigationEventArgs e)
        {
            // TODO: Prepare page for display here.

            // TODO: If your application contains multiple pages, ensure that you are
            // handling the hardware Back button by registering for the
            // Windows.Phone.UI.Input.HardwareButtons.BackPressed event.
            // If you are using the NavigationHelper provided by some templates,
            // this event is handled for you.
        }

        private void AddThread(object sender, RoutedEventArgs e)
        {
            MainThreadCollection.Add(new ThreadViewItem() { Name = "Tom Riddle", LatestMessage = "It worked!" });
        }
    }

    public class ThreadCollection : ObservableCollection<ThreadViewItem>
    {
        public ThreadCollection()
            : base()
        {
            Add(new ThreadViewItem() { Name = "Harry Potter", LatestMessage = "What's up?" });
        }
    }

    public class ThreadViewItem
    {
        public String Name
        {
            get;
            set;
        }

        public String LatestMessage
        {
            get;
            set;
        }
    }
}

因为设计视图正确地预览了来自哈利波特的信息，我认为问题相对较小，我只是无法弄清楚究竟是什么。

Answer 1

我将ThreadCollection放在自己的文件中（最好是ThreadCollection.cs）并将其放在自己的命名空间中，如 Messaging_2._0.Collections 或类似的东西。然后将xmlns：c指向该命名空间。

这将确保您的课程不受编码XAML时所涉及的自动代码生成的影响。

如果它没有解决您的问题，错误文本可能至少会更有帮助。

xaml中的未知类型错误，其类派生自ObservableCollection

1 个答案: