Question

很抱歉，如果这是一个重复的问题。围绕这个主题有很多问题，但我似乎无法弄明白。我正在尝试将列表框绑定到ObservableCollection，并在项目添加到集合时保持列表框更新。

我有一个名为CollectionOfBlogs的课程：

Public Class CollectionOfBlogs
    Implements INotifyPropertyChanged

    Public Event PropertyChanged As PropertyChangedEventHandler _
    Implements INotifyPropertyChanged.PropertyChanged

    Public Sub New(ByVal name As String)
        Me.FullName = name
    End Sub

    Private _FullName As String
    Public Property FullName() As String
        Get
            Return _FullName
        End Get
        Set(ByVal value As String)
            _FullName = value
            NotifyPropertyChanged("FullName")
        End Set
    End Property

    Public Sub NotifyPropertyChanged(ByVal propertyName As String)
        RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs(propertyName))
    End Sub

End Class

然后我在另一个类中设置了CollectionOfBlogs的ObservableCollection（上图）和一个用于向集合中添加项目的子项：

Public Class ITRSBlogs

    Public blogNamesList As New ObservableCollection(Of CollectionOfBlogs)

    Public Sub addBlog(ByVal FullName as String)
        blogNamesList.Add(New CollectionOfBlogs(FullName))
    End Sub

End Class

我将列表框从我的主页加载事件绑定到ITRSBlogs类（上面）中的blogNamesList集合：

Dim blogClass As New ITRSBlogs

Me.BloggingMenuListBox.ItemsSource = blogClass.blogNamesList

这是我的列表框的XAML。它受到代码隐藏的束缚，而不是XAML（我想应该提一下）。

<ListBox Name="BloggingMenuListBox"/>

在将集合绑定到列表框之前，我使用数据库中的项加载集合，它们显示在列表框中就好了。下面的这2个子实际上也在ITRSBlogs类中，我从我的页面加载事件中调用FillBlogLists。

Public Sub FillBlogLists()
    Dim query = theContext.GetBlogsOrderedByNameQuery
    theContext.Load(query, AddressOf OnBlogsLoaded, Nothing)
End Sub

Private Sub OnBlogsLoaded(ByVal lo As LoadOperation(Of Blog))
    blogList.Clear()
    For Each s In lo.AllEntities
        blogList.Add(CType(s, Blog))
    Next
    For Each item In blogList
        blogNamesList.Add(New CollectionOfBlogs(item.FullName))
    Next
End Sub

除此之外，我在页面上有一个简单的文本框和按钮。当在文本框中输入名称并单击该按钮时，我会调用ITRSBlogs类中的addBlog（从文本框中传入名称）子例程（稍微备份页面）以将项目添加到集合中。

问题是，当我向集合添加项目时，列表框不会更新。我是Observable Collections的新手（以及许多其他东西:)，所以也许我真的离开这里。谁能告诉我我做错了什么？

Answer 1

您发布的代码对我来说很好。我复制了你的代码（在C＃中，但我尽量保持它尽可能接近你的代码），它只是起作用。您未发布的唯一代码是Add按钮的事件处理程序。您是否检查过它是否已被实际调用并且新项目已添加到集合中？

无论如何这里是我的代码，也许你可以发现它与你的版本之间的区别：

CollectionOfBlogs.cs：

public class CollectionOfBlogs : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    private string _FullName;
    public string FullName
    {
        get
        {
            return this._FullName;
        }
        set
        {
            if (this._FullName != value)
            {
                this._FullName = value;
                this.OnPropertyChanged("FullName");
            }
        }
    }

    public CollectionOfBlogs(string name)
    {
        this._FullName = name;
    }

    public virtual void OnPropertyChanged(string propertyName)
    {
        if (this.PropertyChanged != null)
        {
            this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }

    public override string ToString()
    {
        return this._FullName;
    }

}

ITRSBlogs.cs：

public class ITRSBlogs
{
    public ObservableCollection<CollectionOfBlogs> blogNamesList = new ObservableCollection<CollectionOfBlogs>();

    public void AddBlog(string fullName)
    {
        this.blogNamesList.Add(new CollectionOfBlogs(fullName));
    }

    public void FillBlogList()
    {
        this.blogNamesList.Clear();
        this.AddBlog("First blog");
        this.AddBlog("Another blog");
    }
}

MainWindow.xaml：

<Window x:Class="ObservableRefreshDemo.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525" Loaded="Window_Loaded">
  <Grid>
    <ListBox Name="BloggingMenuListBox"/>
    <Button Content="Add" Height="23" HorizontalAlignment="Left" Margin="154,276,0,0" Name="button1" VerticalAlignment="Top" Width="75" Click="button1_Click" />
    <TextBox Height="23" HorizontalAlignment="Left" Margin="12,276,0,0" Name="txtName" VerticalAlignment="Top" Width="120" />
  </Grid>
</Window>

MainWindow.xaml.cs：

public partial class MainWindow : Window
{

    private ITRSBlogs blogClass = new ITRSBlogs();

    public MainWindow()
    {
        InitializeComponent();
    }

    private void Window_Loaded(object sender, RoutedEventArgs e)
    {
        this.blogClass.FillBlogList();
        this.BloggingMenuListBox.ItemsSource = this.blogClass.blogNamesList;
    }

    private void button1_Click(object sender, RoutedEventArgs e)
    {
        this.blogClass.AddBlog(this.txtName.Text);
    }
}

列表框绑定到ObservableCollection（在VB.NET和Silverlight中）

1 个答案: