wpf中，一个简单的自定义treeview

首先创建一个自定义控件，在里面定义好treeview的样式，将本来的三角形的图标变为加号的图标，并且添加节点之间的连线。

<UserControl x:Class="TreeViewEx.myTreeView"
             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:i="clr-namespace:TreeViewEx"
             mc:Ignorable="d"
             d:DesignHeight="300" d:DesignWidth="300">
    <UserControl.Resources>
        <i:TreeViewLineConverter x:Key="LineConverter"/>

        <!-- Toggle Button -->
        <Style x:Key="ExpandCollapseToggleStyle" TargetType="ToggleButton">
            <Setter Property="Focusable" Value="False"/>
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="ToggleButton">
                        <Grid Width="20" Height="18" SnapsToDevicePixels="True">
                            <Rectangle Width="12" Height="12" Stroke="#919191" SnapsToDevicePixels="true">
                                <Rectangle.Fill>
                                    <LinearGradientBrush EndPoint="0.5,2" StartPoint="0.5,0">
                                        <GradientStop Color="White" Offset="0"/>
                                        <GradientStop Color="Silver" Offset="0.5"/>
                                        <GradientStop Color="LightGray" Offset="1"/>
                                    </LinearGradientBrush>
                                </Rectangle.Fill>
                            </Rectangle>
                            <Rectangle x:Name="ExpandPath" Width="1" Height="5" Stroke="Black" SnapsToDevicePixels="true"/>
                            <Rectangle Width="5" Height="1" Stroke="Black" SnapsToDevicePixels="true"/>
                        </Grid>
                        <ControlTemplate.Triggers>
                            <Trigger Property="IsChecked" Value="True">
                                <Setter Property="Visibility"  TargetName="ExpandPath" Value="Collapsed"/>
                            </Trigger>
                        </ControlTemplate.Triggers>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>

        <!-- TreeViewItem -->
        <Style x:Key="{x:Type TreeViewItem}" TargetType="{x:Type TreeViewItem}">
            <Setter Property="Background" Value="Transparent"/>
            <Setter Property="Padding" Value="1,0,0,0"/>
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="{x:Type TreeViewItem}">
                        <Grid>
                            <Grid.ColumnDefinitions>
                                <ColumnDefinition MinWidth="19" Width="Auto"/>
                                <ColumnDefinition Width="Auto"/>
                                <ColumnDefinition Width="*"/>
                            </Grid.ColumnDefinitions>
                            <Grid.RowDefinitions>
                                <RowDefinition Height="Auto"/>
                                <RowDefinition/>
                            </Grid.RowDefinitions>

                            <!-- Connecting Lines -->
                            <Rectangle x:Name="HorLn" Margin="9,1,0,0" Height="1" Stroke="#DCDCDC" SnapsToDevicePixels="True"/>
                            <Rectangle x:Name="VerLn" Width="1" Stroke="#DCDCDC" Margin="0,0,1,0" Grid.RowSpan="2" SnapsToDevicePixels="true" Fill="White"/>
                            <ToggleButton Margin="-1,0,0,0" x:Name="Expander" Style="{StaticResource ExpandCollapseToggleStyle}" IsChecked="{Binding Path=IsExpanded, RelativeSource={RelativeSource TemplatedParent}}" ClickMode="Press"/>
                            <Border Name="Bd" Grid.Column="1" Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Padding="{TemplateBinding Padding}" SnapsToDevicePixels="True">
                                <ContentPresenter x:Name="PART_Header" ContentSource="Header" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" MinWidth="20"/>
                            </Border>
                            <ItemsPresenter x:Name="ItemsHost" Grid.Row="1" Grid.Column="1" Grid.ColumnSpan="2"/>
                        </Grid>
                        <ControlTemplate.Triggers>

                            <!-- This trigger changes the connecting lines if the item is the last in the list -->
                            <DataTrigger Binding="{Binding RelativeSource={RelativeSource Self}, Converter={StaticResource LineConverter}}" Value="true">
                                <Setter TargetName="VerLn" Property="Height" Value="9"/>
                                <Setter TargetName="VerLn" Property="VerticalAlignment" Value="Top"/>
                            </DataTrigger>
                            <Trigger Property="IsExpanded" Value="false">
                                <Setter TargetName="ItemsHost" Property="Visibility" Value="Collapsed"/>
                            </Trigger>
                            <Trigger Property="HasItems" Value="false">
                                <Setter TargetName="Expander" Property="Visibility" Value="Hidden"/>
                            </Trigger>
                            <MultiTrigger>
                                <MultiTrigger.Conditions>
                                    <Condition Property="HasHeader" Value="false"/>
                                    <Condition Property="Width" Value="Auto"/>
                                </MultiTrigger.Conditions>
                                <Setter TargetName="PART_Header" Property="MinWidth" Value="75"/>
                            </MultiTrigger>
                            <MultiTrigger>
                                <MultiTrigger.Conditions>
                                    <Condition Property="HasHeader" Value="false"/>
                                    <Condition Property="Height" Value="Auto"/>
                                </MultiTrigger.Conditions>
                                <Setter TargetName="PART_Header" Property="MinHeight" Value="19"/>
                            </MultiTrigger>
                            <Trigger Property="IsSelected" Value="true">
                                <Setter TargetName="Bd" Property="Background" Value="{DynamicResource {x:Static SystemColors.HighlightBrushKey}}"/>
                                <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.HighlightTextBrushKey}}"/>
                            </Trigger>
                            <MultiTrigger>
                                <MultiTrigger.Conditions>
                                    <Condition Property="IsSelected" Value="true"/>
                                    <Condition Property="IsSelectionActive" Value="false"/>
                                </MultiTrigger.Conditions>
                                <Setter TargetName="Bd" Property="Background" Value="Green"/>
                                <Setter Property="Foreground" Value="White"/>
                            </MultiTrigger>
                            <Trigger Property="IsEnabled" Value="false">
                                <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.GrayTextBrushKey}}"/>
                            </Trigger>
                        </ControlTemplate.Triggers>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
    </UserControl.Resources>
    <Grid>
        <TreeView BorderThickness="0">
            <TreeViewItem Header="Program Files">
                <TreeViewItem Header="Header"/>
            </TreeViewItem>
            <TreeViewItem Header="Program Data" IsExpanded="True">
                <TreeViewItem Header="Microsoft">
                    <TreeViewItem Header="Header"/>
                </TreeViewItem>
                <TreeViewItem Header="Microsoft Help"/>
            </TreeViewItem>
            <TreeViewItem Header="Uers" IsExpanded="True">
                <TreeViewItem Header="Default"/>
                <TreeViewItem Header="Public" IsExpanded="True">
                    <TreeViewItem Header="Libraries"/>
                    <TreeViewItem Header="Public Desktop"/>
                    <TreeViewItem Header="Public Documents"/>
                </TreeViewItem>
                <TreeViewItem Header="TUYEN">
                    <TreeViewItem Header="Header"/>
                </TreeViewItem>
            </TreeViewItem>
            <TreeViewItem Header="Windows"/>
        </TreeView>
    </Grid>
</UserControl>

要注意上面的代码中有一句：xmlns:i="clr-namespace:TreeViewEx"，这个TreeViewEx就是这个控件所在的命名空间，在这个控件的后台代码中添加一个类TreeViewLineConverter

class TreeViewLineConverter : IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
            TreeViewItem item = (TreeViewItem)value;
            ItemsControl ic = ItemsControl.ItemsControlFromItemContainer(item);
            return ic.ItemContainerGenerator.IndexFromContainer(item) == ic.Items.Count - ;
        }

        public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
            return false;
        }
    }

这样控件就做完 了，然后在窗口中引用这个控件，同样的需要在窗体文件中添加xmlns:i="clr-namespace:TreeViewEx"。

<Grid>
        <i:myTreeView />

</Grid>