不幸的是，这就是 WPF 的工作方式。如果您想更改默认控件的样式，您很可能必须使用一堆样式声明（如您上面发布的）并对其进行一些更改。
使用 Expression Blend 会让事情变得更容易一些，因为您将拥有一个 UI 设计器，您可以使用它来轻松修改样式。但在幕后，它仍然有样式声明。作为示例，以下是我使用 Blend 满足您的要求的结果：
<Window
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
x:Class="WpfApplication1.MainWindow"
x:Name="Window"
Title="MainWindow"
Width="640" Height="480">
<Window.Resources>
<Style x:Key="TreeViewItemFocusVisual">
<Setter Property="Control.Template">
<Setter.Value>
<ControlTemplate>
<Rectangle/>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
<PathGeometry x:Key="TreeArrow" Figures="M0,0 L0,6 L6,0 z"/>
<Style x:Key="ExpandCollapseToggleStyle" TargetType="{x:Type ToggleButton}">
<Setter Property="Focusable" Value="False"/>
<Setter Property="Width" Value="16"/>
<Setter Property="Height" Value="16"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type ToggleButton}">
<Border Background="Transparent" Height="16" Padding="5,5,5,5" Width="16">
<Image x:Name="PART_Image" Source="Image1.jpg"/>
</Border>
<ControlTemplate.Triggers>
<Trigger Property="IsChecked" Value="False"/>
<Trigger Property="IsMouseOver" Value="True"/>
<Trigger Property="IsChecked" Value="True">
<Setter Property="Source" TargetName="PART_Image" Value="Image2.jpg"/>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
<Style TargetType="{x:Type TreeViewItem}">
<Setter Property="Background" Value="Transparent"/>
<Setter Property="HorizontalContentAlignment" Value="{Binding HorizontalContentAlignment, RelativeSource={RelativeSource AncestorType={x:Type ItemsControl}}}"/>
<Setter Property="VerticalContentAlignment" Value="{Binding VerticalContentAlignment, RelativeSource={RelativeSource AncestorType={x:Type ItemsControl}}}"/>
<Setter Property="Padding" Value="1,0,0,0"/>
<Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.ControlTextBrushKey}}"/>
<Setter Property="FocusVisualStyle" Value="{StaticResource TreeViewItemFocusVisual}"/>
<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>
<ToggleButton x:Name="Expander" ClickMode="Press" IsChecked="{Binding IsExpanded, RelativeSource={RelativeSource TemplatedParent}}" Style="{StaticResource ExpandCollapseToggleStyle}"/>
<Border x:Name="Bd" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" Grid.Column="1" Padding="{TemplateBinding Padding}" SnapsToDevicePixels="true">
<ContentPresenter x:Name="PART_Header" ContentSource="Header" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"/>
</Border>
<ItemsPresenter x:Name="ItemsHost" Grid.ColumnSpan="2" Grid.Column="1" Grid.Row="1"/>
</Grid>
<ControlTemplate.Triggers>
<Trigger Property="IsExpanded" Value="false">
<Setter Property="Visibility" TargetName="ItemsHost" Value="Collapsed"/>
</Trigger>
<Trigger Property="HasItems" Value="false">
<Setter Property="Visibility" TargetName="Expander" Value="Hidden"/>
</Trigger>
<Trigger Property="IsSelected" Value="true">
<Setter Property="Background" TargetName="Bd" 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 Property="Background" TargetName="Bd" Value="{DynamicResource {x:Static SystemColors.ControlBrushKey}}"/>
<Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.ControlTextBrushKey}}"/>
</MultiTrigger>
<Trigger Property="IsEnabled" Value="false">
<Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.GrayTextBrushKey}}"/>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
<Style.Triggers>
<Trigger Property="VirtualizingStackPanel.IsVirtualizing" Value="true">
<Setter Property="ItemsPanel">
<Setter.Value>
<ItemsPanelTemplate>
<VirtualizingStackPanel/>
</ItemsPanelTemplate>
</Setter.Value>
</Setter>
</Trigger>
</Style.Triggers>
</Style>
</Window.Resources>
<Grid x:Name="LayoutRoot">
<TreeView HorizontalAlignment="Left" Margin="8,8,0,105" Width="196">
<TreeViewItem Header="Item1">
<TreeViewItem Header="Item2"/>
</TreeViewItem>
</TreeView>
</Grid>
</Window>
无论如何，我希望这会有所帮助。
EDIT:
好的，我注意到我发布的代码与您在示例中发布的代码非常相似。但我向你保证，我使用了表达式混合来进行上述修改。我想这正好证明了这一点：无论是否使用 Blend，您都必须使用一堆 Style 声明。 =)
EDIT2:
窗口.xaml
<Window x:Class="WpfApplication2.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:WpfApplication2"
xmlns:sys="clr-namespace:System;assembly=mscorlib"
Title="MainWindow" Height="300" Width="300">
<Window.Resources>
<HierarchicalDataTemplate x:Key="treeTemplate"
ItemsSource="{Binding SubItems}">
<TextBlock Text="{Binding Name}"/>
<HierarchicalDataTemplate.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding}"/>
</DataTemplate>
</HierarchicalDataTemplate.ItemTemplate>
</HierarchicalDataTemplate>
<Style x:Key="ExpandCollapseToggleStyle" TargetType="{x:Type ToggleButton}">
<Setter Property="Focusable" Value="False"/>
<Setter Property="Width" Value="16"/>
<Setter Property="Height" Value="16"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type ToggleButton}">
<Border Background="Transparent" Height="16" Width="16">
<Image x:Name="PART_Image" Source="{Binding ImageSource}"/>
</Border>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
<Style x:Key="customTreeItemStyle" TargetType="{x:Type TreeViewItem}">
<Setter Property="IsExpanded" Value="{Binding IsExpanded, Mode=TwoWay}"/>
<Setter Property="Background" Value="Transparent"/>
<Setter Property="HorizontalContentAlignment" Value="{Binding HorizontalContentAlignment, RelativeSource={RelativeSource AncestorType={x:Type ItemsControl}}}"/>
<Setter Property="VerticalContentAlignment" Value="{Binding VerticalContentAlignment, RelativeSource={RelativeSource AncestorType={x:Type ItemsControl}}}"/>
<Setter Property="Padding" Value="1,0,0,0"/>
<Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.ControlTextBrushKey}}"/>
<Setter Property="FocusVisualStyle" Value="{StaticResource TreeViewItemFocusVisual}"/>
<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>
<ToggleButton x:Name="Expander" ClickMode="Press" IsChecked="{Binding IsExpanded, RelativeSource={RelativeSource TemplatedParent}}" Style="{StaticResource ExpandCollapseToggleStyle}"/>
<Border x:Name="Bd" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" Grid.Column="1" Padding="{TemplateBinding Padding}" SnapsToDevicePixels="true">
<ContentPresenter x:Name="PART_Header" ContentSource="Header" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"/>
</Border>
<ItemsPresenter x:Name="ItemsHost" Grid.ColumnSpan="2" Grid.Column="1" Grid.Row="1"/>
</Grid>
<ControlTemplate.Triggers>
<Trigger Property="IsExpanded" Value="false">
<Setter Property="Visibility" TargetName="ItemsHost" Value="Collapsed"/>
</Trigger>
<Trigger Property="HasItems" Value="false">
<Setter Property="Visibility" TargetName="Expander" Value="Hidden"/>
</Trigger>
<Trigger Property="IsSelected" Value="true">
<Setter Property="Background" TargetName="Bd" 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 Property="Background" TargetName="Bd" Value="{DynamicResource {x:Static SystemColors.ControlBrushKey}}"/>
<Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.ControlTextBrushKey}}"/>
</MultiTrigger>
<Trigger Property="IsEnabled" Value="false">
<Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.GrayTextBrushKey}}"/>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
<Style.Triggers>
<Trigger Property="VirtualizingStackPanel.IsVirtualizing" Value="true">
<Setter Property="ItemsPanel">
<Setter.Value>
<ItemsPanelTemplate>
<VirtualizingStackPanel/>
</ItemsPanelTemplate>
</Setter.Value>
</Setter>
</Trigger>
</Style.Triggers>
</Style>
</Window.Resources>
<TreeView x:Name="tree"
ItemTemplate="{StaticResource treeTemplate}"
ItemContainerStyle="{StaticResource customTreeItemStyle}"/>
</Window>
隐藏代码：
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
namespace WpfApplication2
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
private List<ViewModel> items = new List<ViewModel>();
public MainWindow()
{
InitializeComponent();
ViewModelImpl1 vm1 = new ViewModelImpl1() { Name = "VM1" };
vm1.SubItems.Add("SubItem1");
vm1.SubItems.Add("SubItem2");
vm1.SubItems.Add("SubItem3");
ViewModelImpl1 vm2 = new ViewModelImpl1() { Name = "VM2" };
vm2.SubItems.Add("SubItem1");
vm2.SubItems.Add("SubItem2");
vm2.SubItems.Add("SubItem3");
vm2.SubItems.Add("SubItem4");
ViewModelImpl2 vm3 = new ViewModelImpl2() { Name = "VM3" };
vm3.SubItems.Add("SubItem1");
items.Add(vm1);
items.Add(vm2);
items.Add(vm3);
tree.ItemsSource = items;
}
}
}
视图模型
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.ComponentModel;
namespace WpfApplication2
{
public abstract class ViewModel : INotifyPropertyChanged
{
private List<string> subItems = new List<string>();
public List<string> SubItems
{
get { return this.subItems; }
}
private string name;
public string Name
{
get { return this.name; }
set
{
this.name = value;
this.OnPropertyChanged("Name");
}
}
private bool isExpanded;
public bool IsExpanded
{
get { return this.isExpanded; }
set
{
this.isExpanded = value;
this.OnPropertyChanged("IsExpanded");
UpdateImageSource();
}
}
private string imageSource;
public string ImageSource
{
get
{
if (this.imageSource == null)
UpdateImageSource();
return this.imageSource;
}
protected set
{
this.imageSource = value;
this.OnPropertyChanged("ImageSource");
}
}
protected abstract void UpdateImageSource();
#region INotifyPropertyChanged Members
public event PropertyChangedEventHandler PropertyChanged;
private void OnPropertyChanged(string propName)
{
if (this.PropertyChanged != null)
{
this.PropertyChanged(this, new PropertyChangedEventArgs(propName));
}
}
#endregion
}
public class ViewModelImpl1 : ViewModel
{
protected override void UpdateImageSource()
{
if (this.IsExpanded)
this.ImageSource = "pack://application:,,,/Images/bell1.png";
else
this.ImageSource = "pack://application:,,,/Images/bell2.png";
}
}
public class ViewModelImpl2 : ViewModel
{
protected override void UpdateImageSource()
{
if (this.IsExpanded)
this.ImageSource = "pack://application:,,,/Images/star1.png";
else
this.ImageSource = "pack://application:,,,/Images/star2.png";
}
}
}
