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我对 tabcontrol 控制有疑问。

我正在使用绑定和转换器将项目动态添加到 tabcontrol。

添加第二个 tabitem 时出现以下异常（参见下面的代码）：值不在预期范围内

它的堆栈跟踪：

- MS.Internal.XcpImports.CheckHResult(UInt32 hr) - MS.Internal.XcpImports.SetValue(IManagedPeerBase obj, DependencyProperty 属性, DependencyObject doh) - MS.Internal.XcpImports.SetValue(IManagedPeerBase doh, DependencyProperty 属性, Object obj) - System .Windows.DependencyObject.SetObjectValueToCore(DependencyProperty dp, Object value) в System.Windows.DependencyObject.SetEffectiveValue(DependencyProperty property, EffectiveValueEntry& newEntry, Object newValue) в System.Windows.DependencyObject.UpdateEffectiveValue(DependencyProperty property, EffectiveValueEntry oldEntry, EffectiveValueEntry& newEntry, ValueOperation操作）? System.Windows.DependencyObject.SetValueInternal（DependencyProperty dp，对象值，布尔allowReadOnlySet）? System.Windows.Controls.ContentControl。set_Content(Object value) × SilverlightApplication1.Services.TabConverter.Convert(Object value, Type targetType, Object parameter, CultureInfoculture)

主页 xaml：

<UserControl x:Class="SilverlightApplication1.MainPage"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
         xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
         mc:Ignorable="d"
         d:DesignHeight="1024"
         d:DesignWidth="1280"
         xmlns:sdk="http://schemas.microsoft.com/winfx/2006/xaml/presentation/sdk"
         xmlns:local="clr-namespace:SilverlightApplication1.Services">

<UserControl.Resources>
    <local:TabConverter x:Key="tabConverter" />
</UserControl.Resources>

<Grid x:Name="LayoutRoot"
      Background="White">
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="1*" />
        <ColumnDefinition Width="4*" />
    </Grid.ColumnDefinitions>
    <ListBox SelectionChanged="ListBox_SelectionChanged">
        <ListBoxItem Content="ViewA"></ListBoxItem>
        <ListBoxItem Content="ViewB"></ListBoxItem>
    </ListBox>
    <sdk:TabControl Grid.Column="1"
                    ItemsSource="{Binding Tabs, Converter={StaticResource tabConverter}}" />
</Grid>

MainPage 代码隐藏：

    public partial class MainPage : UserControl {
    ViewModel viewModel = new ViewModel();

    public MainPage() {
        InitializeComponent();
        this.DataContext = viewModel;
    }

    private void ListBox_SelectionChanged(object sender, SelectionChangedEventArgs e) {
        try {
            viewModel.Tabs.Add(new TabItemModel() {
                Header = "New Tab",
                Content = new Grid()
            });

            // sdk:tabcontrol does not listen CollectionChanged of viewModel.Tabs.
            // thats why:
            viewModel.Tabs = viewModel.Tabs;
        } catch (Exception) { }
    }
}

数据模型：

 public class TabItemModel {
    public string Header { get; set; }
    public UIElement Content { get; set; }
}

查看型号：

public class ViewModel:INotifyPropertyChanged {
    ObservableCollection<TabItemModel> tabs = new ObservableCollection<TabItemModel>();
    public ObservableCollection<TabItemModel> Tabs {
        get { return tabs; }
        set { tabs = value; OnPropertyChanged(PropertyNames.Tabs); }
    }

    public event PropertyChangedEventHandler PropertyChanged;
    void OnPropertyChanged(string property) {
        if (PropertyChanged != null)
            PropertyChanged(this, new PropertyChangedEventArgs(property));
    }

    class PropertyNames {
        public const string Tabs = "Tabs";
    }
}

标签转换器：

public class TabConverter : IValueConverter {

    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) {
        try {
            var object_data = value as ObservableCollection<TabItemModel>;
            var result = new List<TabItem>();
            foreach (var item in object_data) {
                result.Add(new TabItem() { 
                    Header = item.Header,
                    Content = item.Content // if comment this, everything works
                });
            }
            return result;
        } catch (Exception e) {
            MessageBox.Show(e.StackTrace, e.Message, MessageBoxButton.OK);
            return null;
        }
    }

    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) {
        throw new NotImplementedException();
    }
}
4

1 回答 1

3

您的问题是您UIElement在数据模型中保留了 a 。

在 MVVM 中，这本身就是一个很大的禁忌，但这里的具体问题是，当您添加第二个TabItemModel并且转换器重新创建所有需要TabItem的 s 时，第一个TabItemModel 的内容会立即放置在两个 TabItems 上。单个 UI 元素只能有一个父元素。

这里最“MVVM”的解决方案是将 UI 元素排除在数据模型之外。相反，只需保留一些原始数据TabItemModel.Content并在您的 xaml 中使用DataTemplates 来表示该数据的 UI。

如果您确实需要在数据模型中保留 UI 元素，我建议您看看这个经过调整的 TabControl，它修复了有问题的 Silverlight TabControl，并且不需要转换器才能正常工作：Silverlight TabControl with data binding（从此 SO讨论相同问题的帖子：将 Silverlight TabControl 绑定到集合）

于 2013-05-06T22:31:19.867 回答