WPF TreeView递归异步绑定

WPF的TreeView不像WinForms的TreeView那样，通过TreeNode实现树型节点。WPF的TreeView实现起来，我感觉有点像VM(View-Model)模式，就像WinForms中的DataGrid，控件负责显示，数据在DataTable中。那么我们在实现TreeView时，也需要用这样的思路，数据在Model中，控件是View负责显示。

我需要实现的最终目标是：
1.节点是异步加载的（解决效率问题）
2.节点是无限级别的（递归的，这样可复用与目录结构、组织架构等数据类型）
3.节点是可以多选的（用CheckBox选择）
4.XAML方式绑定（减少UI上Code量）
5.方便得获取选中项信息

先看效果图：


1）数据库设计与准备
为了演示方便，采用了ACCESS数据库，添加一个Department表
表字段：

数据内容：

2）创建WPF项目

3）数据访问类
为了图方便，我采用了Linq to DataSet

 

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using DepartmentTreeView.DB;
using System.Collections;
using DepartmentTreeView.DB.SampleDataSetTableAdapters;

namespace DepartmentTreeView {
    public class DepartmentHelper {

        static SampleDataSet ds = new SampleDataSet();
        static DepartmentTableAdapter da = new DepartmentTableAdapter();

        static DepartmentHelper() {
            da.Fill(ds.Department);
        }

        public static object GetDepartment(int did) {
            var depart = ds.Department.Where(c => c.DID == did).SingleOrDefault();
            return depart;
        }

        public static IEnumerable GetSubDepartments(int pid) {
            var list = ds.Department.Where(c => c.PID == pid).ToList();
            return list;
        }
    }
}

4）创建TreeView 的Model类DepartmentViewModel

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.ComponentModel;
using System.Collections.ObjectModel;

namespace DepartmentTreeView {
    public class DepartmentViewModel:INotifyPropertyChanged {
        //临时子节点用，当Expanded时移除此节点，添加子节点
        static readonly DepartmentViewModel _temp = new DepartmentViewModel(null);
        //选中的子节点
        private static ObservableCollection<DepartmentViewModel> _checkedItems = new ObservableCollection<DepartmentViewModel>();
        //根节点
        static DepartmentViewModel _rootItem;

        #region fields&properties
        private bool? _isChecked;
        public bool? IsChecked {
            get { return _isChecked; }
            set {
                SetCheckState(value, true, true);

            }
        }
        private void SetCheckState(bool? value, bool updateChildren, bool updateParent) {
            if (_isChecked != value) {
                _isChecked = value;

                //通知选中项的集合
                if (_isChecked == true) {
                    _checkedItems.Add(this);
                    PropertyChanged(this, new PropertyChangedEventArgs("CheckedItems"));
                } else if (_isChecked == false) {
                    _checkedItems.Remove(this);
                    PropertyChanged(this, new PropertyChangedEventArgs("CheckedItems"));
                }

                PropertyChanged(this, new PropertyChangedEventArgs("IsChecked"));

                if (updateChildren) {
                    if (HasChildren()) {
                        Children.ForEach(c => c.SetCheckState(value, true, false));
                    }
                }
                if (updateParent && _parent != null) {
                    _parent.VerifyState();
                }
            }
        }
        private void VerifyState() {
            bool? state = null;
            for (int i = 0; i < this.Children.Count; ++i) {
                bool? currentState = this.Children[i].IsChecked;
                if (i == 0) {
                    state = currentState;
                } else if (state != currentState) {
                    state = null;
                    break;
                }
            }
            this.SetCheckState(state, false, true);
        }

        private bool _isExpanded;
        public bool IsExpanded {
            get { return _isExpanded; }
            set {
                if (value != _isExpanded) {
                    _isExpanded = value;
                    PropertyChanged(this, new PropertyChangedEventArgs("IsExpanded"));
                }
                if (!HasChildren()) {
                    Children.Remove(_temp);
                    LoadChildren();
                }
            }
        }

        private object _current;
        public object Current {
            get { return _current; }
            set { _current = value; }
        }
        public string DisplayText {
            get { return ((DepartmentTreeView.DB.SampleDataSet.DepartmentRow)Current)["DName"].ToString(); }
        }

        private DepartmentViewModel _parent;
        public DepartmentViewModel Parent {
            get { return _parent; }
            set { _parent = value; }
        }

        private List<DepartmentViewModel> _children;
        public List<DepartmentViewModel> Children {
            get { return _children; }
            private set { _children = value; }
        }
        #endregion

        public static List<DepartmentViewModel> Create() {
            var list = DepartmentHelper.GetSubDepartments(0);
            DepartmentViewModel root = new DepartmentViewModel(null);
            _rootItem = root;
            root.Children.Clear();
            foreach (var item in list) {
                root.Children.Add(new DepartmentViewModel(item));
            }
            return root.Children;
        }
        private DepartmentViewModel(object currentObject) {
            Current = currentObject;
            _isChecked = false;
            Children = new List<DepartmentViewModel>();
            Children.Add(_temp);
        }

        /// <summary>
        /// 初始化，用于设置父节点
        /// </summary>
        private void Init() {
            if (!HasChildren()) return;
            foreach (DepartmentViewModel child in Children) {
                child.Parent = this;
                child.Init();
            }
            PropertyChanged(this, new PropertyChangedEventArgs("Children"));
        }

        /// <summary>
        /// 加载子节点
        /// </summary>
        private void LoadChildren() {
            if (Current != null) {
                int pid = Convert.ToInt32(((DepartmentTreeView.DB.SampleDataSet.DepartmentRow)Current)["DID"]);
                var list = DepartmentHelper.GetSubDepartments(pid);
                foreach (var item in list) {
                    DepartmentViewModel model = new DepartmentViewModel(item) { _isChecked = this.IsChecked };
                    if (model.IsChecked == true) {
                        _checkedItems.Add(model);
                        PropertyChanged(this, new PropertyChangedEventArgs("CheckedItems"));
                    }
                    Children.Add(model);
                }
                Init();
            }
        }

        /// <summary>
        /// 判断是否有子节点（逻辑是：如果只有一个临时子节点，说明没有真正的子节点）
        /// </summary>
        /// <returns></returns>
        private bool HasChildren() {
            return !(Children.Count == 1 && Children[0] == _temp);
        }

        public ObservableCollection<DepartmentViewModel> CheckedItems {
            get {
                return _checkedItems;
            }
        }

        public event PropertyChangedEventHandler PropertyChanged;
    }
}

5）创建WPF窗体

<Window x:Class="DepartmentTreeView.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:DepartmentTreeView"
        Title="MainWindow" Height="329" Width="212" FontFamily="Arial">
    <Window.Resources>
        <ObjectDataProvider x:Key="depProvider" ObjectType="{x:Type local:DepartmentViewModel}" MethodName="Create" />
        <Style x:Key="TreeViewItemStyle" TargetType="{x:Type TreeViewItem}">
            <Setter Property="IsExpanded" Value="{Binding Path=IsExpanded,Mode=TwoWay}" />
        </Style>
        <HierarchicalDataTemplate x:Key="CheckBoxItemTemplate" ItemsSource="{Binding Children}">
            <StackPanel Orientation="Horizontal" Margin="0,2,0,0">
                <CheckBox Focusable="False" IsChecked="{Binding IsChecked,Mode=TwoWay}" VerticalAlignment="Center" />
                <ContentPresenter Content="{Binding DisplayText,Mode=OneWay}" Margin="2,0" />
            </StackPanel>
        </HierarchicalDataTemplate>
    </Window.Resources>
    <Grid Margin="5">
        <Grid.RowDefinitions>
            <RowDefinition />
            <RowDefinition Height="Auto" />
            <RowDefinition Height="Auto" />
        </Grid.RowDefinitions>
        <TreeView Name="tvDepartment" Grid.Row="0" ItemContainerStyle="{StaticResource TreeViewItemStyle}" ItemsSource="{Binding Source={StaticResource depProvider}}" ItemTemplate="{StaticResource CheckBoxItemTemplate}" />
        <TextBlock Name="tbText" Margin="5" Grid.Row="1">当前选中项：<TextBlock Text="{Binding Source={StaticResource depProvider},Path=CheckedItems.Count,Mode=OneWay,IsAsync=True}" /></TextBlock>
        <Button Margin="5" Grid.Row="2" Content="Get CheckedItems" Click="Button_Click" />
    </Grid>
</Window>

6）窗口的后置代码

using System.Collections.Generic;
using System.Text;
using System.Windows;
using System.Windows.Data;
using System.Windows.Documents;
using System.ComponentModel;

namespace DepartmentTreeView {
    /// <summary>
    /// MainWindow.xaml 的交互逻辑
    /// </summary>
    public partial class MainWindow : Window {
        public MainWindow() {
            InitializeComponent();
        }

        private void Button_Click(object sender, RoutedEventArgs e) {
            ObjectDataProvider provider = FindResource("depProvider") as ObjectDataProvider;
            List<DepartmentViewModel> firstLevelItems = provider.Data as List<DepartmentViewModel>;

            ICollectionView view = CollectionViewSource.GetDefaultView(firstLevelItems);
            DepartmentViewModel rootItem = view.CurrentItem as DepartmentViewModel;

            List<DepartmentViewModel> checkedItems = CollectionViewSource.GetDefaultView(provider) as List<DepartmentViewModel>;

            StringBuilder builder = new StringBuilder();
            foreach (DepartmentViewModel checkItem in rootItem.CheckedItems) {
                builder.AppendLine(checkItem.DisplayText);
            }
            MessageBox.Show("Checked items:/n" + builder.ToString());
        }
    }
}

好了，到此大功告成！！！

源代码：http://download.csdn.net/source/3253097