TreeView单击展开其子元素：

 

在WPF的TreeView控件中，要想展开它的子元素，我们必须要鼠标左键点两下或者右键点一下，那么我们怎样实现左键点一下就使它展开呢？

Xaml：

<Grid>
        <TreeView HorizontalAlignment="Left" Height="208" Margin="243,35,0,0" VerticalAlignment="Top" Width="150">
            <TreeViewItem Header="AAA" Selected="TreeViewItem_Selected">
                <TreeViewItem Header="aaa"/>
                <TreeViewItem Header="bbb"/>
                <TreeViewItem Header="ccc"/>
            </TreeViewItem>
            <TreeViewItem Header="BBB" Selected="TreeViewItem_Selected_1">
                <TreeViewItem Header="aaa"/>
                <TreeViewItem Header="bbb"/>
                <TreeViewItem Header="ccc"/>
            </TreeViewItem>
        </TreeView>
</Grid>

在后台中的TreeViewItem的Selected函数中添加：

    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }

        private void TreeViewItem_Selected(object sender, RoutedEventArgs e)
        {
            TreeViewItem treeViewItem = e.OriginalSource as TreeViewItem;
            if (treeViewItem == null || e.Handled) return;
            treeViewItem.IsExpanded = !treeViewItem.IsExpanded;
            treeViewItem.IsSelected = false;
            e.Handled = true;
        }

        private void TreeViewItem_Selected_1(object sender, RoutedEventArgs e)
        {
            TreeViewItem treeViewItem = e.OriginalSource as TreeViewItem;
            if (treeViewItem == null || e.Handled) return;
            treeViewItem.IsExpanded = !treeViewItem.IsExpanded;
            treeViewItem.IsSelected = false;
            e.Handled = true;
        }
    }

这样就可以实现，左键单击一下TreeViewItem使它子元素直接展开。

如图：

 

点击一个元素展开其他元素收起：

Xaml中：

<Grid>
        <TreeView x:Name="Tree_View" SelectedItemChanged="Tree_View_SelectedItemChanged" HorizontalAlignment="Left" Height="208" Margin="243,35,0,0" VerticalAlignment="Top" Width="150">
            <TreeViewItem Header="AAA" Selected="TreeViewItem_Selected">
                <TreeViewItem Header="aaa"/>
                <TreeViewItem Header="bbb"/>
                <TreeViewItem Header="ccc"/>
            </TreeViewItem>
            <TreeViewItem Header="BBB" Selected="TreeViewItem_Selected_1">
                <TreeViewItem Header="aaa"/>
                <TreeViewItem Header="bbb"/>
                <TreeViewItem Header="ccc"/>
            </TreeViewItem>
        </TreeView>
 </Grid>

就是给TreeView添加了一个SelectedItemChanged属性，当里面的元素状态改变时，执行这个方法。

后台添加的代码：

private void Tree_View_SelectedItemChanged(object sender, RoutedPropertyChangedEventArgs<object> e)
        {
            TreeViewItem selected_item = Tree_View.SelectedItem as TreeViewItem;
            TreeViewItem item;
            if (selected_item != null)
            {
                for (int i = 0; i < Tree_View.Items.Count; i++)
                {
                    item = Tree_View.Items[i] as TreeViewItem;
                    if (item != selected_item)
                    {
                        item.IsExpanded = false;
                    }
                }
            }
        }

注意：我这里的TreeView的Name叫作Tree_View.

这样，就实现了点击一个元素展开其他元素收起的效果。

如图：