VS自带的控件总是觉得不够美观，而xaml语言提供了一个自己编写控件样式的可能性
效果图：
xaml代码：
<ComboBox.Resources><Style TargetType="{x:Type ComboBox}"><Setter Property="Width" Value="120"/><Setter Property="HorizontalAlignment" Value="Stretch"/><Setter Property="Template"><Setter.Value><ControlTemplate TargetType="{x:Type ComboBox}"><Border BorderBrush="White" BorderThickness="2" CornerRadius="22" Background="Transparent"><Grid><!--下拉箭头--><ToggleButton ClickMode="Press" Focusable="False" IsChecked="{Binding IsDropDownOpen, Mode=TwoWay, RelativeSource={RelativeSource TemplatedParent}}" Margin="12" MinWidth="10" MinHeight="0" Width="Auto" Foreground="White"><ToggleButton.Style><Style TargetType="{x:Type ToggleButton}"><Setter Property="MinWidth" Value="0"/><Setter Property="MinHeight" Value="0"/><Setter Property="Width" Value="Auto"/><Setter Property="Height" Value="Auto"/><Setter Property="Background" Value="Transparent"/><Setter Property="BorderBrush" Value="#00000000"/><Setter Property="BorderThickness" Value="2"/><Setter Property="Template"><Setter.Value><ControlTemplate TargetType="{x:Type ToggleButton}"><DockPanel Background="{TemplateBinding Background}" LastChildFill="False" SnapsToDevicePixels="True"><Border x:Name="Border" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" DockPanel.Dock="Right" ><Path Data="M0,0L3.5,4 7,0z" Fill="{TemplateBinding Foreground}" HorizontalAlignment="Center" VerticalAlignment="Center"/></Border></DockPanel><ControlTemplate.Triggers><Trigger Property="IsChecked" Value="True"/></ControlTemplate.Triggers></ControlTemplate></Setter.Value></Setter><Style.Triggers><Trigger Property="IsEnabled" Value="False"><Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.ControlDarkBrushKey}}"/></Trigger></Style.Triggers></Style></ToggleButton.Style></ToggleButton><!--项内容--><ContentPresenter IsHitTestVisible="False" Content="{TemplateBinding SelectionBoxItem}" ContentTemplate="{TemplateBinding SelectionBoxItemTemplate}" ContentTemplateSelector="{TemplateBinding ItemTemplateSelector}" VerticalAlignment="Center" Margin="3" HorizontalAlignment="Stretch" /><TextBox x:Name="PART_EditableTextBox" HorizontalAlignment="Stretch" Focusable="True" Visibility="Collapsed" IsReadOnly="False"/><!--下拉显示面板HorizontalOffset:设置下拉面板的相对位置--><Popup HorizontalOffset="-1" Width="{TemplateBinding ActualWidth}"IsOpen="{TemplateBinding IsDropDownOpen}" Focusable="False" PopupAnimation="Slide"><Grid SnapsToDevicePixels="True" HorizontalAlignment="Stretch"><Border BorderThickness="0,0,0,0" BorderBrush="White" HorizontalAlignment="Stretch" CornerRadius="0" Background="White"/><ScrollViewer SnapsToDevicePixels="True" HorizontalAlignment="Stretch" ><StackPanel IsItemsHost="True" KeyboardNavigation.DirectionalNavigation="Contained" HorizontalAlignment="Stretch" /></ScrollViewer></Grid></Popup></Grid></Border></ControlTemplate></Setter.Value></Setter></Style></ComboBox.Resources><ComboBox.Background><LinearGradientBrush EndPoint="0,1" StartPoint="0,10"><GradientStop Color="White" Offset="0"/><GradientStop Color="White" Offset="1"/></LinearGradientBrush></ComboBox.Background><ComboBoxItem Content="管理员" Foreground="#FF505050" BorderThickness="0"/><ComboBoxItem Content="操作员" Foreground="#FF505050" BorderThickness="0" BorderBrush="White" Background="White"/></ComboBox>
