C# 使用HierarchycalDataTemplate的WPF MVVM树视图未更新

因此，我一直在努力让我的TreeView正确更新很长一段时间了，所以我问是否有人可以告诉我为什么我的代码没有正确更新我的TreeView节点的加法或减法。我为有点大的代码转储提前道歉，但我觉得说明这个问题非常重要

首先，我的ObservieObject类

public abstract class ObservableObject : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    [NotifyPropertyChangedInvocator]
    protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
    {
        PropertyChangedEventHandler handler = this.PropertyChanged;
        if (handler != null)
        {
            handler(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}

TreeNodeBase类

public abstract class TreeNodeBase : ObservableObject
{
    protected const string ChildNodesPropertyName = "ChildNodes";

    protected string name;

    public string Name
    {
        get
        {
            return this.name;
        }

        set
        {
            this.name = value;
            this.OnPropertyChanged();
        }
    }

    protected IList<TreeNode> childNodes;

    protected TreeNodeBase(string name)
    {
        this.Name = name;
        this.childNodes = new List<TreeNode>();
    }

    public IEnumerable<TreeNode> ChildNodes
    {
        get
        {
            return this.childNodes;
        }
    }

    public TreeNodeBase AddChildNode(string name)
    {
        var treeNode = new TreeNode(this, name);
        this.childNodes.Add(treeNode);
        this.OnPropertyChanged(ChildNodesPropertyName);

        return treeNode;
    }

    public TreeNode RemoveChildNode(string name)
    {
        var nodeToRemove = this.childNodes.FirstOrDefault(node => node.Name.Equals(name));

        if (nodeToRemove != null)
        {
            this.childNodes.Remove(nodeToRemove);
            this.OnPropertyChanged(ChildNodesPropertyName);
        }

        return nodeToRemove;
    }
}

public class TreeNode : TreeNodeBase
{
    public TreeNodeBase Parent { get; protected set; }

    public TreeNode(TreeNodeBase parent, string name)
        : base(name)
    {
        this.Parent = parent;
    }
}

TreeNode类

public class TreeNode : TreeNodeBase
{
    public TreeNodeBase Parent { get; protected set; }

    public TreeNode(TreeNodeBase parent, string name)
        : base(name)
    {
        this.Parent = parent;
    }
}

TreeView用户控件Xaml

<UserControl x:Class="TreeViewExperiment.TreeView"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
             xmlns:treeViewExperiment="clr-namespace:TreeViewExperiment"
             xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"
             mc:Ignorable="d" 
             d:DesignHeight="300" d:DesignWidth="400"
             d:DataContext="{d:DesignInstance treeViewExperiment:TreeViewmodel}">

    <UserControl.DataContext>
        <treeViewExperiment:TreeViewmodel/>
    </UserControl.DataContext>

    <Grid Background="White">
        <Grid.Resources>
            <HierarchicalDataTemplate x:Key="TreeViewHierarchicalTemplate" ItemsSource="{Binding ChildNodes}">
                <TextBlock Text="{Binding Name}"/>
            </HierarchicalDataTemplate>

            <Style TargetType="Button">
                <Setter Property="FontFamily" Value="Verdana"/>
                <Setter Property="FontWeight" Value="Bold"/>
            </Style>
        </Grid.Resources>
        <Grid.RowDefinitions>
            <RowDefinition Height="6*"/>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="Auto"/>
        </Grid.RowDefinitions>
        <TreeView Grid.Row="0" x:Name="Tree" ItemsSource="{Binding RootLevelNodes}" ItemTemplate="{StaticResource TreeViewHierarchicalTemplate}">
            <i:Interaction.Triggers>
                <i:EventTrigger EventName="SelectedItemChanged">
                    <i:InvokeCommandAction
                        Command="{Binding SetSelectedNode}"
                        CommandParameter="{Binding SelectedItem, ElementName=Tree}"/>
                </i:EventTrigger>
            </i:Interaction.Triggers>
        </TreeView>

        <Grid Grid.Row="1" Height="25">
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="4*"/>
                <ColumnDefinition Width="2*"/>
                <ColumnDefinition Width="2*"/>
            </Grid.ColumnDefinitions>

            <TextBox x:Name="NameTextBox" Grid.Column="0" VerticalAlignment="Center" FontFamily="Verdana"/>
            <Button Grid.Column="1" Content="Add Node" Command="{Binding AddNode}" CommandParameter="{Binding Text, ElementName=NameTextBox}" Background="Green"/>
            <Button Grid.Column="2" Content="Remove Node" Command="{Binding RemoveNode}" Background="Red"/>
        </Grid>
    </Grid>
</UserControl>

最后是TreeViewmodel

public class TreeViewmodel : ObservableObject
{
    public ICommand SetSelectedNode { get; private set; }

    public ICommand AddNode { get; private set; }

    public ICommand RemoveNode { get; private set; }

    public TreeViewmodel()
    {
        this.SetSelectedNode = new ParamaterizedDelegateCommand(
            node =>
                {
                    this.SelectedTreeNode = (TreeNodeBase)node;
                });

        this.AddNode = new ParamaterizedDelegateCommand(name => this.SelectedTreeNode.AddChildNode((string)name));

        this.RemoveNode = new DelegateCommand(
            () =>
                {
                    if (selectedTreeNode.GetType() == typeof(TreeNode))
                    {
                        var parent = ((TreeNode)this.SelectedTreeNode).Parent;
                        parent.RemoveChildNode(this.SelectedTreeNode.Name);
                        this.SelectedTreeNode = parent;
                    }
                });

        var adam = new TreeViewRoot("Adam");
        var steve = adam.AddChildNode("Steve");
        steve.AddChildNode("Jack");

        this.rootLevelNodes = new List<TreeViewRoot> { adam, new TreeViewRoot("Eve") };
    }

    private TreeNodeBase selectedTreeNode;

    private readonly IList<TreeViewRoot> rootLevelNodes;

    public IEnumerable<TreeViewRoot> RootLevelNodes
    {
        get
        {
            return this.rootLevelNodes;
        }
    }

    public TreeNodeBase SelectedTreeNode
    {
        get
        {
            return this.selectedTreeNode;
        }

        set
        {
            this.selectedTreeNode = value;
            this.OnPropertyChanged();
        }
    }
}

public类TreeViewmodel:observeObject
{
public ICommand SetSelectedNode{get；private set；}
public ICommand AddNode{get；private set；}
public ICommand RemoveNode{get；private set；}
公共树视图模型（）
{
this.SetSelectedNode=新的paramaterizeddelgateCommand(
节点=>
{
this.SelectedTreeNode=（TreeNodeBase）节点；
});
this.AddNode=new ParamaterizedDelegateCommand（name=>this.SelectedTreeNode.AddChildNode（（字符串）name））；
this.RemoveNode=新的DelegateCommand(
() =>
{
if（selectedTreeNode.GetType（）==typeof（TreeNode））
{
var parent=（（TreeNode）this.SelectedTreeNode）.parent；
parent.RemoveChildNode（this.SelectedTreeNode.Name）；
this.SelectedTreeNode=parent；
}
});
var adam=新树的树根（“adam”）；
var steve=adam.AddChildNode（“steve”）；
steve.AddChildNode（“杰克”）；
this.rootLevelNodes=新列表{adam，new TreeViewRoot（“Eve”）}；
}
私有树根据选择的树节点；
私有只读IList rootLevelNodes；
公共IEnumerable RootLevelNodes
{
得到
{
返回this.rootLevelNodes；
}
}
公共树使用选定的树节点
{
得到
{
返回此。selectedTreeNode；
}
设置
{
this.selectedTreeNode=值；
this.OnPropertyChanged（）；
}
}
}

因此，我知道当添加或删除子元素时，UI应该得到通知，因为当我调试它时，我可以看到在这两种情况下都调用了ChildNodes属性上的get访问器，但UI上显示的内容保持不变

---

在过去，我已经解决了这个问题，但是使用了ObservableCollections，这似乎是StackOverflow这类问题的大多数解决方案所指向的，但是为什么这个解决方案也不起作用呢？我遗漏了什么？

问题是您误用了

INotifyPropertyChanged

。在代码中，您正在通知视图您的属性

ChildNodes

已更改，但它不是真的，因为

treevieItem.ItemsSource

仍然等于您的

ChildNodes

属性

INotifyPropertyChanged

将在视图模型中的基础集合对象更改时导致UI更新

要在集合中出现新项目时更新

ItemsSource

，需要使用实现

INotifyCollectionChanged

的集合

作为：

可以枚举实现IEnumerable接口的任何集合。但是，要设置动态绑定以便集合中的插入或删除自动更新UI，集合必须实现INotifyCollectionChanged接口。此接口公开一个事件，该事件应在基础集合发生更改时引发

这就是为什么SO上的每个人都建议使用

ObservableCollection

编辑：

---

如果要公开只读集合，则应选中。它可以作为

observateCollection

的包装，可以将其公开。

这似乎就是问题所在。然而，对于我来说，远离ObservableCollection仍然很重要，因为我想向UI公开一个只读的集合。我可能会把现有的列表分解到它自己的类中，它实现了IntIfyCopyCaldC改接口，看看这是怎么回事。也许你应该考虑使用？

public class TreeViewmodel : ObservableObject
{
    public ICommand SetSelectedNode { get; private set; }

    public ICommand AddNode { get; private set; }

    public ICommand RemoveNode { get; private set; }

    public TreeViewmodel()
    {
        this.SetSelectedNode = new ParamaterizedDelegateCommand(
            node =>
                {
                    this.SelectedTreeNode = (TreeNodeBase)node;
                });

        this.AddNode = new ParamaterizedDelegateCommand(name => this.SelectedTreeNode.AddChildNode((string)name));

        this.RemoveNode = new DelegateCommand(
            () =>
                {
                    if (selectedTreeNode.GetType() == typeof(TreeNode))
                    {
                        var parent = ((TreeNode)this.SelectedTreeNode).Parent;
                        parent.RemoveChildNode(this.SelectedTreeNode.Name);
                        this.SelectedTreeNode = parent;
                    }
                });

        var adam = new TreeViewRoot("Adam");
        var steve = adam.AddChildNode("Steve");
        steve.AddChildNode("Jack");

        this.rootLevelNodes = new List<TreeViewRoot> { adam, new TreeViewRoot("Eve") };
    }

    private TreeNodeBase selectedTreeNode;

    private readonly IList<TreeViewRoot> rootLevelNodes;

    public IEnumerable<TreeViewRoot> RootLevelNodes
    {
        get
        {
            return this.rootLevelNodes;
        }
    }

    public TreeNodeBase SelectedTreeNode
    {
        get
        {
            return this.selectedTreeNode;
        }

        set
        {
            this.selectedTreeNode = value;
            this.OnPropertyChanged();
        }
    }
}