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SelecteItem我正在尝试在其属性上使用带有数据绑定的 WPF 组合框。当用户选择一个新的选择时，会SelectedItem发生变化，但我的模型没有正确更新，并且SelectionBoxItem（组合框中显示的项目）没有改变。

更具体地说，我有以下两个元素：

<ListView Name="lvNodes" ItemsSource="{Binding Path=Nodes}" SelectedItem="{Binding Path=CurrentNode, Mode=TwoWay}">
                    <ListView.ItemTemplate>
                        <DataTemplate>
                            <StackPanel Orientation="Horizontal">
                                <TextBlock Text="{Binding Path=Name}"/>
                            </StackPanel>
                        </DataTemplate>
                    </ListView.ItemTemplate>
                </ListView>

此列表视图按预期工作。有问题的组合框是这样定义的

<ComboBox ItemsSource="{Binding Path=CameraViews}" SelectedItem="{Binding Path=CurrentNode.NodeInfo.Camera1, Converter={StaticResource EnsureBlank}, Mode=TwoWay}" Name="comboBoxTopCam" SelectionChanged="comboBoxTopCam_SelectionChanged">
                                <ComboBox.ItemTemplate>
                                    <DataTemplate>
                                        <TextBlock Text="{Binding Path=Name}"/>
                                    </DataTemplate>
                                </ComboBox.ItemTemplate>
                            </ComboBox>

因此，当用户从 ListView（上图）中选择一个节点时，ComboBox 会更新以显示该节点正在使用的相机。

现在奇怪的行为。如果用户单击组合框上的新项目，我可以停止调试器并检查该SelecteItem属性。这总是被正确设置，但是CurrentNode.NodeInfo.Camera1属性没有改变，并且“SelectionBox”中显示的字符串没有改变。

然而，它变得更加陌生。如果用户在 ComboBox 上进行此类选择之后切换节点（使用前面定义的 ListView），则 ComboBox 再次不会显示新值，但这SelectedItem是正确的。如果用户随后再次更改 ListView 中的选定项目，则它开始显示正确的值，并且在用户再次弄乱组合框之前很好。

现在我之前说过，当 ComboBox 更改时，我的模型不会更新，所以我制作了一个事件处理程序来为我更新模型（您可以在 ComboBox 的定义中看到这一点）。这被定义为可能

private void comboBoxTopCam_SelectionChanged(object sender, SelectionChangedEventArgs e)
    {
        CameraViewInfo selCam = comboBoxTopCam.SelectedItem as CameraViewInfo;
        if (selCam != null)
        {
            OTNode selNode = lvNodes.SelectedItem as OTNode;

            if (selCam.Name == "None")
                selNode.NodeInfo.Camera1 = new CameraViewInfo();
            else
                selNode.NodeInfo.Camera1 = selCam; // <- This line affects the behavior
        }
    }

当我注释掉上面列表中的标记行时，ComboBox 会在 SelectionBox 中显示正确的项目，但不会更新我的模型（例如CurrentNode.NodeInfo.Camera1未更改）。当我使用lvNodes.SelectedItemOR 时会发生这种情况CurrentCamera（数据绑定属性），这没有区别。

我知道这是一个非常奇怪的问题，我尽我所能解释它，如果有人想要更多信息（数据绑定的调试输出、转换器的代码、关于相等运算符的信息等）我很乐意提供它，我会如有必要，活动愿意上传显示奇怪行为的视频，因为仅从文本中很难理解。

更新：

转换器代码

public class EnsureBlankConterter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        if (value is CameraViewInfo)
        {
            if ((value as CameraViewInfo).Name == "")
            {
                return new CameraViewInfo()
                {
                    Name = "None"
                };
            }
        }

        return value;
    }

    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        if (value is CameraViewInfo)
        {
            if ((value as CameraViewInfo).Name == "None")
            {
                return new CameraViewInfo();
            }
        }

        return value;
    }
}

调试输出使用PresentationTraceSource.High

加载时：

System.Windows.Data Warning: 54 : Created BindingExpression (hash=45045097) for Binding (hash=10919470)
System.Windows.Data Warning: 56 :   Path: 'CurrentNode.NodeInfo.Camera1'
System.Windows.Data Warning: 60 : BindingExpression (hash=45045097): Attach to System.Windows.Controls.ComboBox.SelectedItem (hash=34909671)
System.Windows.Data Warning: 65 : BindingExpression (hash=45045097): Resolving source 
System.Windows.Data Warning: 68 : BindingExpression (hash=45045097): Found data context element: ComboBox (hash=34909671) (OK)
System.Windows.Data Warning: 76 : BindingExpression (hash=45045097): Activate with root item ConfigurationWindow (hash=22010384)
System.Windows.Data Warning: 105 : BindingExpression (hash=45045097):   At level 0 using cached accessor for ConfigurationWindow.CurrentNode: RuntimePropertyInfo(CurrentNode)
System.Windows.Data Warning: 102 : BindingExpression (hash=45045097): Replace item at level 0 with ConfigurationWindow (hash=22010384), using accessor RuntimePropertyInfo(CurrentNode)
System.Windows.Data Warning: 99 : BindingExpression (hash=45045097): GetValue at level 0 from ConfigurationWindow (hash=22010384) using RuntimePropertyInfo(CurrentNode): <null>
System.Windows.Data Warning: 104 : BindingExpression (hash=45045097):   Item at level 1 is null - no accessor
System.Windows.Data Warning: 101 : BindingExpression (hash=45045097): Replace item at level 2 with {NullDataItem}
System.Windows.Data Warning: 78 : BindingExpression (hash=45045097): TransferValue - got raw value {DependencyProperty.UnsetValue}
System.Windows.Data Warning: 86 : BindingExpression (hash=45045097): TransferValue - using fallback/default value <null>
System.Windows.Data Warning: 87 : BindingExpression (hash=45045097): TransferValue - using final value <null>
System.Windows.Data Warning: 99 : BindingExpression (hash=45045097): GetValue at level 0 from ConfigurationWindow (hash=22010384) using RuntimePropertyInfo(CurrentNode): OTNode (hash=59090892)
System.Windows.Data Warning: 99 : BindingExpression (hash=45045097): GetValue at level 0 from ConfigurationWindow (hash=22010384) using RuntimePropertyInfo(CurrentNode): OTNode (hash=59090892)
System.Windows.Data Warning: 106 : BindingExpression (hash=45045097):   At level 1 - for OTNode.NodeInfo found accessor ReflectPropertyDescriptor(NodeInfo)
System.Windows.Data Warning: 102 : BindingExpression (hash=45045097): Replace item at level 1 with OTNode (hash=59090892), using accessor ReflectPropertyDescriptor(NodeInfo)
System.Windows.Data Warning: 99 : BindingExpression (hash=45045097): GetValue at level 1 from OTNode (hash=59090892) using ReflectPropertyDescriptor(NodeInfo): OTNodeInfo (hash=34742292)
System.Windows.Data Warning: 106 : BindingExpression (hash=45045097):   At level 2 - for OTNodeInfo.Camera1 found accessor ReflectPropertyDescriptor(Camera1)
System.Windows.Data Warning: 102 : BindingExpression (hash=45045097): Replace item at level 2 with OTNodeInfo (hash=34742292), using accessor ReflectPropertyDescriptor(Camera1)
System.Windows.Data Warning: 99 : BindingExpression (hash=45045097): GetValue at level 2 from OTNodeInfo (hash=34742292) using ReflectPropertyDescriptor(Camera1): CameraViewInfo (hash=29245900)
System.Windows.Data Warning: 78 : BindingExpression (hash=45045097): TransferValue - got raw value CameraViewInfo (hash=29245900)
System.Windows.Data Warning: 80 : BindingExpression (hash=45045097): TransferValue - user's converter produced CameraViewInfo (hash=29245900)
System.Windows.Data Warning: 87 : BindingExpression (hash=45045097): TransferValue - using final value CameraViewInfo (hash=29245900)

在选择框中未显示的组合框上进行选择后：

System.Windows.Data Warning: 88 : BindingExpression (hash=45045097): Update - got raw value CameraViewInfo (hash=7936647)
System.Windows.Data Warning: 90 : BindingExpression (hash=45045097): Update - user's converter produced CameraViewInfo (hash=7936647)
System.Windows.Data Warning: 92 : BindingExpression (hash=45045097): Update - using final value CameraViewInfo (hash=7936647)
System.Windows.Data Warning: 99 : BindingExpression (hash=45045097): GetValue at level 0 from ConfigurationWindow (hash=22010384) using RuntimePropertyInfo(CurrentNode): OTNode (hash=59090892)
System.Windows.Data Warning: 99 : BindingExpression (hash=45045097): GetValue at level 1 from OTNode (hash=59090892) using ReflectPropertyDescriptor(NodeInfo): OTNodeInfo (hash=22129877)

将 ListView 切换到新节点，Selection Box 仍然没有更新：

System.Windows.Data Warning: 99 : BindingExpression (hash=45045097): GetValue at level 0 from ConfigurationWindow (hash=22010384) using RuntimePropertyInfo(CurrentNode): OTNode (hash=63206919)
System.Windows.Data Warning: 99 : BindingExpression (hash=45045097): GetValue at level 0 from ConfigurationWindow (hash=22010384) using RuntimePropertyInfo(CurrentNode): OTNode (hash=63206919)
System.Windows.Data Warning: 106 : BindingExpression (hash=45045097):   At level 1 - for OTNode.NodeInfo found accessor ReflectPropertyDescriptor(NodeInfo)
System.Windows.Data Warning: 102 : BindingExpression (hash=45045097): Replace item at level 1 with OTNode (hash=63206919), using accessor ReflectPropertyDescriptor(NodeInfo)
System.Windows.Data Warning: 99 : BindingExpression (hash=45045097): GetValue at level 1 from OTNode (hash=63206919) using ReflectPropertyDescriptor(NodeInfo): OTNodeInfo (hash=35582358)
System.Windows.Data Warning: 106 : BindingExpression (hash=45045097):   At level 2 - for OTNodeInfo.Camera1 found accessor ReflectPropertyDescriptor(Camera1)
System.Windows.Data Warning: 102 : BindingExpression (hash=45045097): Replace item at level 2 with OTNodeInfo (hash=35582358), using accessor ReflectPropertyDescriptor(Camera1)
System.Windows.Data Warning: 99 : BindingExpression (hash=45045097): GetValue at level 2 from OTNodeInfo (hash=35582358) using ReflectPropertyDescriptor(Camera1): CameraViewInfo (hash=49590542)
System.Windows.Data Warning: 78 : BindingExpression (hash=45045097): TransferValue - got raw value CameraViewInfo (hash=49590542)
System.Windows.Data Warning: 80 : BindingExpression (hash=45045097): TransferValue - user's converter produced CameraViewInfo (hash=49590542)
System.Windows.Data Warning: 87 : BindingExpression (hash=45045097): TransferValue - using final value CameraViewInfo (hash=49590542)

使用 DID 更新选择框的列表视图切换节点后：

System.Windows.Data Warning: 99 : BindingExpression (hash=51217614): GetValue at level 0 from ConfigurationWindow (hash=63245828) using RuntimePropertyInfo(CurrentNode): OTNode (hash=8023662)
System.Windows.Data Warning: 99 : BindingExpression (hash=51217614): GetValue at level 0 from ConfigurationWindow (hash=63245828) using RuntimePropertyInfo(CurrentNode): OTNode (hash=8023662)
System.Windows.Data Warning: 106 : BindingExpression (hash=51217614):   At level 1 - for OTNode.NodeInfo found accessor ReflectPropertyDescriptor(NodeInfo)
System.Windows.Data Warning: 102 : BindingExpression (hash=51217614): Replace item at level 1 with OTNode (hash=8023662), using accessor ReflectPropertyDescriptor(NodeInfo)
System.Windows.Data Warning: 99 : BindingExpression (hash=51217614): GetValue at level 1 from OTNode (hash=8023662) using ReflectPropertyDescriptor(NodeInfo): OTNodeInfo (hash=21425964)
System.Windows.Data Warning: 106 : BindingExpression (hash=51217614):   At level 2 - for OTNodeInfo.Camera1 found accessor ReflectPropertyDescriptor(Camera1)
System.Windows.Data Warning: 102 : BindingExpression (hash=51217614): Replace item at level 2 with OTNodeInfo (hash=21425964), using accessor ReflectPropertyDescriptor(Camera1)
System.Windows.Data Warning: 99 : BindingExpression (hash=51217614): GetValue at level 2 from OTNodeInfo (hash=21425964) using ReflectPropertyDescriptor(Camera1): CameraViewInfo (hash=6049320)
System.Windows.Data Warning: 78 : BindingExpression (hash=51217614): TransferValue - got raw value CameraViewInfo (hash=6049320)
System.Windows.Data Warning: 80 : BindingExpression (hash=51217614): TransferValue - user's converter produced CameraViewInfo (hash=6049320)
System.Windows.Data Warning: 87 : BindingExpression (hash=51217614): TransferValue - using final value CameraViewInfo (hash=6049320)
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3 回答 3

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我认为您的问题在于您绑定到的方式SelectedItem：

<ComboBox ...
    SelectedItem="{Binding Path=CurrentNode.NodeInfo.Camera1, 
        Converter={StaticResource EnsureBlank}, Mode=TwoWay}"  ...

如果内存服务正确，SelectedItem一个属性（Text是另一个）（默认情况下）仅在失去焦点时推送更新。

添加UpdateSourceTrigger="PropertyChanged"到绑定以强制更新更频繁地发生。你不应该需要你的活动。

于 2012-09-29T01:45:00.747 回答
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好的，所以我最终完全摆脱了数据绑定，并使用了一个非常 winforms 风格的事件模型来更新我的数据。我仍然无法弄清楚为什么数据绑定不起作用，如果有人有使用数据绑定的解决方案，我会接受它作为答案。

于 2012-10-03T13:31:34.760 回答
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您的转换器会创建一个新对象，而 ItemTemplate 的 TextBlock 中的文本仍绑定到原始对象。因此，很明显，当您更改新对象的 Name 属性时，它不会改变。

于 2012-09-29T09:51:04.627 回答