Question

我有一个自定义控件ChatTextControl，其中包含2个textbox和一个button。 xaml就像这样：

<Grid Background="White">
    <Grid.ColumnDefinitions>
        <!-- Message -->
        <ColumnDefinition Width="*"/>
        <!-- delete message -->
        <ColumnDefinition Width="Auto"/>
    </Grid.ColumnDefinitions>
    <!-- Message content -->
    <StackPanel>
        <TextBlock Text="{Binding Path= Pseudo}" FontWeight="SemiBold"/>
        <TextBlock Text="{Binding Path= Message}" TextWrapping="Wrap"/>
    </StackPanel>

    <Button Grid.Column="1" Padding="8" VerticalAlignment="Top" Width="20" Height="20" Background="{x:Null}" Click="Button_Click"/>
</Grid>

伪和消息来自以下类：

public class ChatListItemViewModel : BaseViewModel
{
    public string Pseudo { get; set; }

    public string Message { get; set; }

    public int Id { get; set; }
}

在另一个自定义控件ChatTextControl中调用

ChatListControl：

<Grid Background="White">
    <ScrollViewer VerticalScrollBarVisibility="Auto">
        <ItemsControl ItemsSource="{Binding Items}">
            <ItemsControl.ItemTemplate>
                <DataTemplate>
                    <local:ChatTextControl />
                </DataTemplate>
            </ItemsControl.ItemTemplate>
        </ItemsControl>
    </ScrollViewer>
</Grid>

在主窗口中，我这样叫ChatListControl：

<local:ChatListControl x:Name="MyChat" Margin="389,10,10,38"/>

并在后面的代码中设置DataContext：

ChatListModel chat = new ChatListModel();
MyChat.DataContext = chat;

ChatListModel：

public class ChatListModel : ChatListViewModel
{
    private static int idCount = 0;

    public ChatListModel()
    {
        Items = new List<ChatListItemViewModel>();
    }

    public void AddMessage(string p, string m)
    {
        Items.Add(new ChatListItemViewModel
        {
            Pseudo = p,
            Message = m,
            Id = idCount
        });
        idCount++;
    }
}

目标是使用ChatTextControl中的Button_Click事件来删除列表中具有相应ID的元素。但是我不知道如何在ChatTextControl.cs或MainWindow.cs中获得代码背后的ID。

如果有人知道该怎么做或对删除按钮有更好的主意，请告诉我。

Answer 1

例如，您可以在单击按钮时在IsDelete中设置ChatListItemViewModel属性，在ChatListModel中引发事件并处理该事件。您需要使用ObservableCollecton<T>而不是List<T>才能在视图中删除该项目：

public class ChatListModel : ChatListViewModel
{
    private static int idCount = 0;

    public ChatListModel()
    {
        Items = new ObservableCollection<ChatListItemViewModel>();
        AddMessage("p", "m");
    }

    public void AddMessage(string p, string m)
    {
        ChatListItemViewModel newItem = new ChatListItemViewModel
        {
            Pseudo = p,
            Message = m,
            Id = idCount
        };
        newItem.PropertyChanged += NewItem_PropertyChanged;
        Items.Add(newItem);
        idCount++;
    }

    private void NewItem_PropertyChanged(object sender, PropertyChangedEventArgs e)
    {
        ChatListItemViewModel removedItem = (ChatListItemViewModel)sender;
        removedItem.PropertyChanged -= NewItem_PropertyChanged;
        Items.Remove(removedItem);
        idCount--;
    }

    public ObservableCollection<ChatListItemViewModel> Items { get; }
}

public class ChatListItemViewModel : BaseViewModel
{
    public string Pseudo { get; set; }

    public string Message { get; set; }

    public int Id { get; set; }

    private bool _isDeleted;
    public bool IsDeleted
    {
        get { return _isDeleted; }
        set { _isDeleted = value; OnPropertyChanged(nameof(IsDeleted)); }
    }

    public ChatListItemViewModel()
    {
        DeleteCommand = new RelayCommand(_ => true, _ => IsDeleted = true);
    }

    public ICommand DeleteCommand { get; }
}

ChatTextControl.xaml：

<Button Grid.Column="1" Padding="8" VerticalAlignment="Top" Width="20" Height="20" 
        Background="{x:Null}" Command="{Binding DeleteCommand}" />

Answer 2

由于评论中的原因，我无法验证mm8的答案，所以这是我找到的解决方案。

在Break_Click事件中放置断点后，我注意到可以通过将ChatListItemViewModel强制转换为this.DataContext并发送如下事件来获取ChatTextControl的ID：

    public delegate void DeleteClick(int id);
    public static event DeleteClick OnDeleteClick;
    private void Button_Click(object sender, System.Windows.RoutedEventArgs e)
    {
        OnDeleteClick?.Invoke(((ChatListItemViewModel)this.DataContext).Id);
    }

这样做，我可以获取ID并在主窗口中删除该项目：

    public ChatListModel chat;
    public MainWindow()
    {
        InitializeComponent();
        chat = new ChatListModel();
        chat.AddMessage(name, "Hello World!");
        MyChat.DataContext = chat;
        ChatTextControl.OnDeleteClick += ChatTextControl_OnDeleteClick;
    }

    private void ChatTextControl_OnDeleteClick(int id)
    {
        chat.DelMessage(id);
        MyChat.DataContext = null;
        MyChat.DataContext = chat;
    }

C＃WPF如何在后面的代码中获取绑定值

2 个答案: