没有使用Silverlight的ItemsControl Canvas.TopProperty和Canvas.LeftProperty

我想创建一个画布，用户可以在其中删除UI元素（表示任务）。然后他可以拖动它们来重新排列它们。元素包含在DataContext的ObservableCollection中。 我可以设置Canvas的Left和Top属性，但对象位置不受影响。有任何想法吗？ 谢谢， 卡雷尔 更新： forgotton ItemsControl后裔（谢谢菲尔）： 
 public class CustomItemsCollection    : ItemsControl
{
    protected override void PrepareContainerForItemOverride(DependencyObject element, object item)
    {            
        FrameworkElement contentitem = element as FrameworkElement;
        // contentitem.HorizontalAlignment = System.Windows.HorizontalAlignment.Left;
        // contentitem.VerticalAlignment = System.Windows.VerticalAlignment.Top;
        Binding leftBinding = new Binding("Left"); 
        leftBinding.Mode = BindingMode.TwoWay;

        contentitem.SetBinding(Canvas.LeftProperty, leftBinding);

        Binding topBinding = new Binding("Top");
        topBinding.Mode = BindingMode.TwoWay;
        contentitem.SetBinding(Canvas.TopProperty, topBinding);
        base.PrepareContainerForItemOverride(element, item);
    }
}
更多信息： 从usercontrol派生的绑定对象会引发异常，所以在一些谷歌搜索后我创建了一个valueconverter： 
public class UIElementWrapper : IValueConverter
{
    private Dictionary<object, object> CollectionsPool = new Dictionary<object, object>();

    #region IValueConverter Members

    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        if (value is INotifyCollectionChanged && value is IList)
        {
            ((INotifyCollectionChanged)value).CollectionChanged += UIElementWrapper_CollectionChanged;

            var result = new ObservableCollection<ProxyObject>();
            foreach (var item in (IList)value)
            {
                result.Add(new ProxyObject(item));
            }

            CollectionsPool.Add(result, value);
            return result;
        }
        else
        {
            throw new ArgumentException("value");
        }
    }

    void UIElementWrapper_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
    {
        if (CollectionsPool.ContainsValue(sender))
        {
            foreach (IList result in CollectionsPool.Keys)
            {
                if (CollectionsPool[result] == sender)
                {
                    switch (e.Action)
                    {
                        case NotifyCollectionChangedAction.Add:
                            var index = e.NewStartingIndex;
                            foreach (var item in e.NewItems)
                            {
                                result.Insert(index++, new ProxyObject(item));
                            }
                            break;
                        case NotifyCollectionChangedAction.Remove:
                            foreach (var item in e.OldItems)
                            {
                                var deleteList = new List<ProxyObject>();
                                foreach (ProxyObject p in result)
                                {
                                    if (p.Value == item) deleteList.Add(p);
                                }
                                foreach (var p in deleteList)
                                {
                                    result.Remove(p);
                                }
                            }
                            break;
                        case NotifyCollectionChangedAction.Replace:
                            result[e.OldStartingIndex] = new ProxyObject(e.NewItems[0]);
                            break;
                        case NotifyCollectionChangedAction.Reset:
                            result.Clear();
                            break;
                        default:
                            break;
                    }
                }
            }
        }
    }

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

    #endregion
}

public class ProxyObject
{
    public ProxyObject(object value)
    {
        Value = value;
    }
    public object Value { get; private set; }
}
这有效。 但是当我绑定ObservableCollection中包含的元素的Left和Top属性时，它们不被使用：所有项目都放在位置0,0 这是后面的代码： 
public MainPage()
    {
        InitializeComponent();

        ObservableCollection<Border> items = new ObservableCollection<Border>();
        double left = 0.0;
        double top = 0.0;
        int i = 0;
        Border item = (Border)XamlReader.Load(
           "<Border Background="Green" Height="140" Width="180"  xmlns="http://schemas.microsoft.com/client/2007"></Border>");
        item.Name = string.Format("name {0}", i);
        item.SetValue(Canvas.LeftProperty, left);
        item.SetValue(Canvas.TopProperty, top);
        items.Add(item);

        i++;
        left += 200;
        top += 150;
        item = (Border)XamlReader.Load(
            "<Border Background="Yellow" Margin="160, 120, 0, 0" Height="120" Width="160"  xmlns="http://schemas.microsoft.com/client/2007"></Border>");
        item.Name = string.Format("name {0}", i);
        item.SetValue(Canvas.LeftProperty, left);
        item.SetValue(Canvas.TopProperty, top);
        items.Add(item);

        i++;
        left += 170;
        top += 130;
        item = (Border)XamlReader.Load(
            "<Border Background="Red" Height="60" Width="80"  xmlns="http://schemas.microsoft.com/client/2007"></Border>");
        item.Name = string.Format("name {0}", i);
        item.SetValue(Canvas.LeftProperty, left);
        item.SetValue(Canvas.TopProperty, top);
        items.Add(item);

        left += 90;
        top += 70;
        item = (Border)XamlReader.Load(
            "<Border Background="Blue" Height="30" Width="40"  xmlns="http://schemas.microsoft.com/client/2007"></Border>");
        item.Name = string.Format("name {0}", i);

        item.SetValue(Canvas.LeftProperty, left);
        item.SetValue(Canvas.TopProperty, top);
        items.Add(item);



        try
        {
            // this.customItemsCollection1.ItemsSource = items;
            LayoutRoot.DataContext = items;
        }
        catch (Exception ex)
        {
            textBlock1.Text = ex.Message;
        }
    }
这是xaml： 
<UserControl x:Class="ItemsControlTestProject.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"
xmlns:lh="clr-namespace:ItemsControlTestProject.Helpers"
         mc:Ignorable="d"
d:DesignHeight="450" d:DesignWidth="560" xmlns:my="clr-namespace:ItemsControlTestProject">


<UserControl.Resources>
        <lh:UIElementWrapper x:Key="UIElementWrapper"/>
    </UserControl.Resources>
    <Grid x:Name="LayoutRoot" Background="AntiqueWhite">
            <my:CustomItemsCollection Canvas.Left="0" Canvas.Top="0" Background="Coral" x:Name="customItemsCollection1" Margin="0,0,0,0" Width="532" ItemsSource="{Binding Converter={StaticResource UIElementWrapper}}">
                <ItemsControl.ItemsPanel>
                    <ItemsPanelTemplate>
                        <Canvas   Background="LightGoldenrodYellow" Canvas.Left="0" Canvas.Top="0" Width="350" Height="350"/>
                    </ItemsPanelTemplate>
                </ItemsControl.ItemsPanel>
                <ItemsControl.ItemTemplate>
                    <DataTemplate>
                        <ContentPresenter Content="{Binding Value}"  Canvas.Left="{Binding Left}" Canvas.Top="{Binding Top}" />
                    </DataTemplate>
                </ItemsControl.ItemTemplate>
        </my:CustomItemsCollection>
            <TextBlock  Height="61" Name="textBlock1" Text="TextBlock" AllowDrop="True" Width="526" Canvas.Left="6" Canvas.Top="367" Margin="20,388,14,0" />        
    </Grid>
</UserControl>





<UserControl.Resources>
        <lh:UIElementWrapper x:Key="UIElementWrapper"/>
    </UserControl.Resources>
    <Grid x:Name="LayoutRoot" Background="AntiqueWhite">
            <my:CustomItemsCollection Canvas.Left="0" Canvas.Top="0" Background="Coral" x:Name="customItemsCollection1" Margin="0,0,0,0" Width="532" ItemsSource="{Binding Converter={StaticResource UIElementWrapper}}">
                <ItemsControl.ItemsPanel>
                    <ItemsPanelTemplate>
                        <Canvas   Background="LightGoldenrodYellow" Canvas.Left="0" Canvas.Top="0" Width="350" Height="350"/>
                    </ItemsPanelTemplate>
                </ItemsControl.ItemsPanel>
                <ItemsControl.ItemTemplate>
                    <DataTemplate>
                        <ContentPresenter Content="{Binding Value}"  Canvas.Left="{Binding Left}" Canvas.Top="{Binding Top}" />
                    </DataTemplate>
                </ItemsControl.ItemTemplate>
        </my:CustomItemsCollection>
            <TextBlock  Height="61" Name="textBlock1" Text="TextBlock" AllowDrop="True" Width="526" Canvas.Left="6" Canvas.Top="367" Margin="20,388,14,0" />        
    </Grid>
</UserControl>
    
2019-06-21 2 条评论
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没有找到相关结果

    已邀请:

    靛取糕奖穿

    问题是您在绑定之前设置依赖项属性Canvas.Top，方法是将其添加到集合中。在此“添加”之前，您绑定的对象没有属性Canvas.Top 只需更改订单 
    items.Add(item);
item.SetValue(Canvas.LeftProperty, left);
item.SetValue(Canvas.TopProperty, top);
    ..它应该工作 / Nykkel     
    2019-06-21 0 0
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