Silverlight：將UIElement綁定到ListBoxItems時發生TargetInvocationException

Question

我創建一個ListBox並將ItemsSource綁定到對象列表：

MainPage.xaml ：

<Grid x:Name="LayoutRoot" Background="White"
         DataContext="{StaticResource ResourceKey=ViewModel}">

        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="47*"/>
            <ColumnDefinition Width="28*"/>
        </Grid.ColumnDefinitions>

        <ListBox ItemsSource="{Binding Models}"
                     Height="200" Width="150"  Grid.Column="0">
            <ListBox.ItemTemplate>
                <DataTemplate >
                    <StackPanel>
                        <TextBlock Text="{Binding ID ,Mode=TwoWay 
                              ,UpdateSourceTrigger=PropertyChanged}"/>
                        <TextBlock Text="{Binding Name ,Mode=TwoWay 
                              ,UpdateSourceTrigger=PropertyChanged}"/>
                        <Border Child="{Binding Shape ,Mode=TwoWay 
                              ,UpdateSourceTrigger=PropertyChanged}"/>

                    </StackPanel>
                </DataTemplate>
            </ListBox.ItemTemplate>
        </ListBox>

        <Button Content="Change Source" Height="35" Width="100" 
                Grid.Column="1">
            <i:Interaction.Triggers>
                <i:EventTrigger EventName="Click">
                    <i:InvokeCommandAction Command="{Binding  ChangeSource}"  
                    CommandParameter="{Binding ElementName=LayoutRoot}" />
                </i:EventTrigger>
            </i:Interaction.Triggers>
        </Button>

    </Grid>

Model.cs ：

public class Model
{
    private string _ID;
    private UIElement _Shape;
    private string _Name;

    public string Name
    {
        get { return _Name; }
        set { _Name = value; }
    }

    public UIElement Shape
    {
        get { return _Shape; }
        set { _Shape = value;}
    }

    public string ID
    {
        get { return _ID; }
        set { _ID = value; }
    }
}

和

ViewModel.cs ：

    public class ViewModel : INotifyPropertyChanged
    {
        Random rnd = new Random();
        List<Color> MyColors = new List<Color>() { Colors.Gray,
                               Colors.Blue, Colors.Red,
                               Colors.Green, Colors.Yellow, 
                               Colors.Orange, Colors.DarkGray };

        private List<Model> _Models;

        public List<Model> Models
        {
            get 
            {
                if (_Models == null)
                    _Models = new List<Model>();
                return _Models;
            }
            set { _Models = value; OnPropertyChanged("Models"); }
        }

        public DelegateCommand<object> ChangeSource { get; set; }

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


        public ViewModel()
        {
            ChangeSource = new DelegateCommand<object>(ChangeSourceCommand);

            ChangeSourceItems();
        }

        private void ChangeSourceCommand(object obj)
        {
            ChangeSourceItems();
        }
        private void ChangeSourceItems()
        {
            List<Model> tmpModels = new List<Model>();

            tmpModels.Add(new Model() { ID = "1", Name = "A", Shape = new Border() { Background = new SolidColorBrush(MyColors[rnd.Next(0, MyColors.Count - 1)]), Width = 10, Height = 10 } });
            tmpModels.Add(new Model() { ID = "2", Name = "B", Shape = new Border() { Background = new SolidColorBrush(MyColors[rnd.Next(0, MyColors.Count - 1)]), Width = 10, Height = 10 } });
            tmpModels.Add(new Model() { ID = "3", Name = "C", Shape = new Border() { Background = new SolidColorBrush(MyColors[rnd.Next(0, MyColors.Count - 1)]), Width = 10, Height = 10 } });
            tmpModels.Add(new Model() { ID = "4", Name = "D", Shape = new Border() { Background = new SolidColorBrush(MyColors[rnd.Next(0, MyColors.Count - 1)]), Width = 10, Height = 10 } });
            tmpModels.Add(new Model() { ID = "5", Name = "E", Shape = new Border() { Background = new SolidColorBrush(MyColors[rnd.Next(0, MyColors.Count - 1)]), Width = 10, Height = 10 } });
            tmpModels.Add(new Model() { ID = "6", Name = "F", Shape = new Border() { Background = new SolidColorBrush(MyColors[rnd.Next(0, MyColors.Count - 1)]), Width = 10, Height = 10 } });

            Models = tmpModels;
        }
    }

單擊Button更改模型的來源。

問題 ：

單擊Button並滾動ListView之后發生TargetInvocationException 。 為什么？

異常消息 ：

調用的目標已引發異常。

InnerException消息 ：

值不在預期范圍內。

Answer 1

因為您在模型中使用UIElement ，所以多次創建形狀並滾動發生TargetInvocationException 。

您必須繼承ListBox並重寫IsItemItsOwnContainerOverride方法。

protected override bool IsItemItsOwnContainerOverride(object item)
{
     Model model = (Model)item;

     FrameworkElement elem = (FrameworkElement)model.Shape;

     return elem.Parent != null;
}