使用wpf写一个treeview 可以自由添加节点，删除，双击等操作,使用mvvm格式

首先，我们需要在ViewModel中定义一个类来表示树节点，例如：

public class TreeNodeViewModel : INotifyPropertyChanged
{
    private string _text;
    private ObservableCollection<TreeNodeViewModel> _children;

    public string Text
    {
        get { return _text; }
        set
        {
            if (_text != value)
            {
                _text = value;
                OnPropertyChanged(nameof(Text));
            }
        }
    }

    public ObservableCollection<TreeNodeViewModel> Children
    {
        get { return _children; }
        set
        {
            if (_children != value)
            {
                _children = value;
                OnPropertyChanged(nameof(Children));
            }
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;

    protected virtual void OnPropertyChanged(string propertyName)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}

然后，我们在MainViewModel中定义一个ObservableCollection<TreeNodeViewModel>来表示树的根节点，以及一些方法来添加/删除节点和处理双击事件：

public class MainViewModel : INotifyPropertyChanged
{
    private ObservableCollection<TreeNodeViewModel> _rootNodes;

    public ObservableCollection<TreeNodeViewModel> RootNodes
    {
        get { return _rootNodes; }
        set
        {
            if (_rootNodes != value)
            {
                _rootNodes = value;
                OnPropertyChanged(nameof(RootNodes));
            }
        }
    }

    public MainViewModel()
    {
        RootNodes = new ObservableCollection<TreeNodeViewModel>();
    }

    public void AddNode(TreeNodeViewModel parent, string text)
    {
        if (parent == null)
        {
            RootNodes.Add(new TreeNodeViewModel { Text = text, Children = new ObservableCollection<TreeNodeViewModel>() });
        }
        else
        {
            parent.Children.Add(new TreeNodeViewModel { Text = text, Children = new ObservableCollection<TreeNodeViewModel>() });
        }
    }

    public void RemoveNode(TreeNodeViewModel node)
    {
        if (node == null)
        {
            return;
        }

        if (node == RootNodes.FirstOrDefault())
        {
            RootNodes.Remove(node);
        }
        else
        {
            var parent = FindParentNode(RootNodes, node);
            if (parent != null)
            {
                parent.Children.Remove(node);
            }
        }
    }

    public void HandleDoubleClick(TreeNodeViewModel node)
    {
        // handle double click event
    }

    private TreeNodeViewModel FindParentNode(IEnumerable<TreeNodeViewModel> nodes, TreeNodeViewModel child)
    {
        foreach (var node in nodes)
        {
            if (node == child || node.Children == null)
            {
                continue;
            }

            if (node.Children.Contains(child))
            {
                return node;
            }

            var parent = FindParentNode(node.Children, child);
            if (parent != null)
            {
                return parent;
            }
        }

        return null;
    }

    public event PropertyChangedEventHandler PropertyChanged;

    protected virtual void OnPropertyChanged(string propertyName)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}

最后，我们可以在View中使用TreeView控件来显示树，并将其绑定到MainViewModel中的RootNodes属性。我们还可以为TreeViewItem添加双击事件处理程序，以及为ContextMenu添加添加/删除节点的菜单项。

<TreeView ItemsSource="{Binding RootNodes}">
    <TreeView.ItemTemplate>
        <HierarchicalDataTemplate ItemsSource="{Binding Children}">
            <TextBlock Text="{Binding Text}" />
        </HierarchicalDataTemplate>
    </TreeView.ItemTemplate>
    <TreeView.ItemContainerStyle>
        <Style TargetType="{x:Type TreeViewItem}">
            <EventSetter Event="MouseDoubleClick" Handler="TreeViewItem_DoubleClick" />
            <Setter Property="ContextMenu">
                <Setter.Value>
                    <ContextMenu>
                        <MenuItem Header="Add Node" Command="{Binding AddNodeCommand}" />
                        <MenuItem Header="Remove Node" Command="{Binding RemoveNodeCommand}" />
                    </ContextMenu>
                </Setter.Value>
            </Setter>
        </Style>
    </TreeView.ItemContainerStyle>
</TreeView>