【发布时间】：2015-10-08 23:10:45
【问题描述】：
我在这个非常好的article 的帮助下构建了一个 treeView WPF MVVM 然后我为某个节点创建了一个 contextMenu，允许我从选定的父节点添加子节点。
问题是如果我点击“添加”而不手动展开选定的节点（父节点），除了点击“添加”时预期生成的节点外，还会自动创建一个奇怪的子节点。
我试图检测问题，因此我将以下代码更改为：
<Setter Property="IsExpanded" Value="{Binding IsExpanded, Mode=TwoWay}" />
到：
<Setter Property="IsExpanded" Value="True" />
下面的图 1 显示了此测试的结果，或者图 2 显示了我的 treeView 必须显示的内容。
Rq：我使用了我谈到的article 中的图像。另外，我使用了文章中描述的相同方法（包括类 TreeViewItemViewModel.cs ）
-
所有 ViewModel 的基类
公共类 TreeViewItemViewModel : INotifyPropertyChanged { #region 数据
static readonly TreeViewItemViewModel DummyChild = new TreeViewItemViewModel(); readonly ObservableCollection<TreeViewItemViewModel> _children; readonly TreeViewItemViewModel _parent; bool _isExpanded; bool _isSelected; #endregion // Data #region Constructors protected TreeViewItemViewModel(TreeViewItemViewModel parent, bool lazyLoadChildren) { _parent = parent; _children = new ObservableCollection<TreeViewItemViewModel>(); if (lazyLoadChildren) _children.Add(DummyChild); } // This is used to create the DummyChild instance. private TreeViewItemViewModel() { } #endregion // Constructors #region Presentation Members #region Children /// <summary> /// Returns the logical child items of this object. /// </summary> public ObservableCollection<TreeViewItemViewModel> Children { get { return _children; } } #endregion // Children #region HasLoadedChildren /// <summary> /// Returns true if this object's Children have not yet been populated. /// </summary> public bool HasDummyChild { get { return this.Children.Count == 1 && this.Children[0] == DummyChild; } } #endregion // HasLoadedChildren #region IsExpanded /// <summary> /// Gets/sets whether the TreeViewItem /// associated with this object is expanded. /// </summary> public bool IsExpanded { get { return _isExpanded; } set { if (value != _isExpanded) { _isExpanded = value; this.OnPropertyChanged("IsExpanded"); } // Expand all the way up to the root. if (_isExpanded && _parent != null) _parent.IsExpanded = true; // Lazy load the child items, if necessary. if (this.HasDummyChild) { this.Children.Remove(DummyChild); this.LoadChildren(); } } } #endregion // IsExpanded #region IsSelected /// <summary> /// Gets/sets whether the TreeViewItem /// associated with this object is selected. /// </summary> public bool IsSelected { get { return _isSelected; } set { if (value != _isSelected) { _isSelected = value; this.OnPropertyChanged("IsSelected"); } } } #endregion // IsSelected #region LoadChildren /// <summary> /// Invoked when the child items need to be loaded on demand. /// Subclasses can override this to populate the Children collection. /// </summary> protected virtual void LoadChildren() { } #endregion // LoadChildren #region Parent public TreeViewItemViewModel Parent { get { return _parent; } } #endregion // Parent #endregion // Presentation Members #region INotifyPropertyChanged Members public event PropertyChangedEventHandler PropertyChanged; protected virtual void OnPropertyChanged(string propertyName) { if (this.PropertyChanged != null) this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName)); } #endregion // INotifyPropertyChanged Members}
Myxml：
<TreeView ItemsSource="{Binding Regions}" IsEnabled="{Binding EnableTree}" >
<TreeView.ItemContainerStyle>
<!--
This Style binds a TreeViewItem to a TreeViewItemViewModel.
-->
<Style TargetType="{x:Type TreeViewItem}">
<Setter Property="IsExpanded" Value="{Binding IsExpanded, Mode=TwoWay}" />
<Setter Property="IsSelected" Value="{Binding IsSelected, Mode=TwoWay}" />
<Setter Property="FontWeight" Value="Normal" />
<Style.Triggers>
<Trigger Property="IsSelected" Value="True">
<Setter Property="FontWeight" Value="Bold" />
</Trigger>
</Style.Triggers>
</Style>
</TreeView.ItemContainerStyle>
<TreeView.Resources>
<ContextMenu x:Key="AddCity" ItemsSource="{Binding AddCityItems}"/>
<HierarchicalDataTemplate
DataType="{x:Type local:StateViewModel}"
ItemsSource="{Binding Children}"
>
<StackPanel Orientation="Horizontal" ContextMenu="{StaticResource AddCity}">
<Image Width="16" Height="16" Margin="3,0" Source="Images\Region.png" />
<TextBlock Text="{Binding RegionName}" />
</StackPanel>
</HierarchicalDataTemplate>
</TreeView.Resources>
- RegionViewModel：
`公共类StateViewModel：TreeViewItemViewModel {
readonly State _state;
public ICommand AddCityCommand { get; private set; }
public List<MenuItem> AddCityItems { get; set; }
public StateViewModel(State state, RegionViewModel parentRegion)
: base(parentRegion, true)
{
_state = state;
AddCityItems = new List<MenuItem>();
AddCityCommand = new DelegateCommand<CancelEventArgs>(OnAddCityCommandExecute, OnAddCityCommandCanExecute);
AddCityItems.Add(new MenuItem() { Header = "Add City", Command = AddCityCommand });
}
public string StateName
{
get { return _state.StateName; }
}
protected override void LoadChildren()
{
foreach (City city in Database.GetCities(_state))
base.Children.Add(new CityViewModel(city, this));
}
bool OnAddCityCommandCanExecute(CancelEventArgs parameter)
{
return true;
}
public void OnAddCityCommandExecute(CancelEventArgs parameter)
{
var myNewCity = new city();
Children.Add(new CityViewModel(myNewCity, this));
}
}`
顺便说一句，如果我展开我的父节点然后我点击添加城市，我得到了预期的结果，但是如果我不展开父节点并且我点击 contextMenu，除了我想要的孩子之外，我还创建了另一个孩子创建
编辑 我将下面的语句添加到我的 add() 方法中，现在我没有任何问题：
public void OnAddCityCommandExecute(CancelEventArgs parameter)
{
var myNewCity = new city();
Children.Add(new CityViewModel(myNewCity, this));
//the modif
this.Children.Remove(DummyChild);
}
【问题讨论】：
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代码在哪里？
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我可以看到您直接绑定到 ViewModel 对象，因为您的节点在 Image1 中显示文本。输出只是 ViewModel.ToString()。在您将 xmal 和 ViewModel 进行审核之前，我们无法为您提供帮助
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@cscmh99，我给了你我用它来创建我的 TreeView 的文章。我使用了完全相同的代码。那么，如果我们拥有所有源代码，我为什么要放置我的代码。 ！您能否解释一下“我直接绑定 ViewModel 对象”是什么意思！
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@EmpereurAiman 你可以打开上面的文章
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@SADOK 您可以发布最低限度的代码让我们理解，而无需阅读一篇大文章。请参阅：stackoverflow.com/help/mcve