C# MVVM侧边导航栏TreeView代码展开箭头靠右

要实现C# MVVM侧边导航栏TreeView代码展开箭头靠右，可以通过自定义TreeView控件的ItemTemplate来实现。

首先，在XAML中定义TreeView控件的ItemTemplate，可以参考如下代码：

<TreeView ItemsSource="{Binding TreeViewItems}">
    <TreeView.ItemTemplate>
        <HierarchicalDataTemplate ItemsSource="{Binding Children}">
            <Grid>
                <Grid.ColumnDefinitions>
                    <ColumnDefinition Width="Auto"/>
                    <ColumnDefinition Width="*"/>
                </Grid.ColumnDefinitions>
                <Image Grid.Column="0" Source="{Binding Icon}" Width="16" Height="16"/>
                <TextBlock Grid.Column="1" Text="{Binding Name}"/>
            </Grid>
            <HierarchicalDataTemplate.ItemContainerStyle>
                <Style TargetType="{x:Type TreeViewItem}">
                    <Setter Property="HorizontalContentAlignment" Value="Stretch"/>
                    <Setter Property="VerticalContentAlignment" Value="Center"/>
                    <Setter Property="Padding" Value="2,0,0,0"/>
                </Style>
            </HierarchicalDataTemplate.ItemContainerStyle>
        </HierarchicalDataTemplate>
    </TreeView.ItemTemplate>
</TreeView>

其中，TreeViewItems是ViewModel中绑定的TreeView数据源，包括每个节点的图标、名称和子节点等信息。

接下来，在TreeViewItem的样式中设置展开/折叠箭头靠右对齐：

<Style TargetType="{x:Type TreeViewItem}">
    <Setter Property="HorizontalContentAlignment" Value="Stretch"/>
    <Setter Property="VerticalContentAlignment" Value="Center"/>
    <Setter Property="Padding" Value="2,0,0,0"/>
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="{x:Type TreeViewItem}">
                <Grid>
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="Auto"/>
                        <ColumnDefinition Width="*"/>
                        <ColumnDefinition Width="Auto"/>
                    </Grid.ColumnDefinitions>
                    <ToggleButton x:Name="Expander" ClickMode="Press" IsChecked="{Binding IsExpanded, RelativeSource={RelativeSource TemplatedParent}}" Style="{StaticResource ExpandCollapseToggleStyle}"/>
                    <Border x:Name="Bd" Grid.Column="1" Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Padding="{TemplateBinding Padding}">
                        <ContentPresenter x:Name="PART_Header" ContentSource="Header" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}"/>
                    </Border>
                    <ItemsPresenter x:Name="ItemsHost" Grid.Column="1" Grid.Row="1" Visibility="Collapsed"/>
                </Grid>
                <ControlTemplate.Triggers>
                    <Trigger Property="IsExpanded" Value="true">
                        <Setter TargetName="ItemsHost" Property="Visibility" Value="Visible"/>
                    </Trigger>
                    <MultiTrigger>
                        <MultiTrigger.Conditions>
                            <Condition Property="HasItems" Value="false"/>
                            <Condition Property="IsSelected" Value="true"/>
                        </MultiTrigger.Conditions>
                        <Setter TargetName="Bd" Property="Background" Value="{DynamicResource {x:Static SystemColors.HighlightBrushKey}}"/>
                        <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.HighlightTextBrushKey}}"/>
                    </MultiTrigger>
                    <MultiTrigger>
                        <MultiTrigger.Conditions>
                            <Condition Property="HasItems" Value="true"/>
                            <Condition Property="IsSelected" Value="true"/>
                        </MultiTrigger.Conditions>
                        <Setter TargetName="Bd" Property="Background" Value="{DynamicResource {x:Static SystemColors.HighlightBrushKey}}"/>
                        <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.HighlightTextBrushKey}}"/>
                    </MultiTrigger>
                    <Trigger Property="IsEnabled" Value="false">
                        <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.GrayTextBrushKey}}"/>
                    </Trigger>
                </ControlTemplate.Triggers>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

其中，Expander定义了展开/折叠状态，通过Grid.Column="0"将其放置在第一列；Bd定义了节点名称区域，通过Grid.Column="1"将其放置在第二列；ItemsPresenter定义了子节点列表，通过Grid.Column="1"和Grid.Row="1"将其放置在第二行；通过Grid.ColumnDefinitions定义了三列，第一列为展开/折叠箭头，第二列为节点名称区域，第三列留空。

这样，展开/折叠箭头就会靠右对齐了。