How to style ComboBox Background on Mouse Hover?

I have a Rounded Border that contains a ComboBox

<Border CornerRadius="10"  BorderBrush...>
   <ComboBox Background="{x:Null}">
      <ComboBoxItem ...>
      <ComboBoxItem ...>
   </ComboBox>
</Border>

When my mouse is not hovering on top of the Combobox, it looks nice and transparent. Like this:

When the mouse hovers on it, it then produce the old, Button-like, background, like this:

I would like the ComboBox to have with a transparent background even when mouse is hoving on top. I tried various ways including writing MouseEnter, MouseLeave, MouseMove to set the background to null, but with no success.

private void ComboBox_MouseEnter(object sender, RoutedEventArgs e)
{
   comboBox1.Background = null;
}

I then try to set the Styling:

<Window.Resources>
    <Style TargetType="{x:Type ComboBox}" x:Key="HoverBox">
        <Style.Triggers>
            <Trigger Property="IsMouseOver" Value="True">
                <Setter Property="Background" Value="Pink" />
            </Trigger>
        </Style.Triggers>
    </Style>
</Window.Resources&g开发者_JAVA技巧t;

that didn't work either. Then I tried modifying the control template:

<ControlTemplate TargetType="{x:Type ComboBox}" x:Key="MouseHover">
    <ControlTemplate.Triggers>
        <Trigger Property="IsMouseOver" Value="True">
            <Setter Property="Background" Value="Red" />
            <Setter Property="Foreground" Value="Green" />
        </Trigger>
    </ControlTemplate.Triggers>
</ControlTemplate>

Worst, after I modify the Control template the ComboBox disappear, like follow:

I have done everything possible, but I am still getting that ugly button-background on my ComboBox whenever my mouse is hover on it.

Anyone knows what's going wrong here?

Check your Previous Posts asking the same

Unable to style WPF ComboBox on Mouse Hover

How to change ComboBox's Background Property during Mouse Hover

EDIT

Use like this. Below is the default controltemplate of the combobox. Note the commented line of code for your requirement

   <Window.Resources>
        <!-- Fill Brushes -->

        <LinearGradientBrush x:Key="NormalBrush" StartPoint="0,0" EndPoint="0,1">
            <GradientBrush.GradientStops>
                <GradientStopCollection>
                    <GradientStop Color="#FFF" Offset="0.0"/>
                    <GradientStop Color="#CCC" Offset="1.0"/>
                </GradientStopCollection>
            </GradientBrush.GradientStops>
        </LinearGradientBrush>

        <LinearGradientBrush x:Key="HorizontalNormalBrush" StartPoint="0,0" EndPoint="1,0">
            <GradientBrush.GradientStops>
                <GradientStopCollection>
                    <GradientStop Color="#FFF" Offset="0.0"/>
                    <GradientStop Color="#CCC" Offset="1.0"/>
                </GradientStopCollection>
            </GradientBrush.GradientStops>
        </LinearGradientBrush>

        <LinearGradientBrush x:Key="LightBrush" StartPoint="0,0" EndPoint="0,1">
            <GradientBrush.GradientStops>
                <GradientStopCollection>
                    <GradientStop Color="#FFF" Offset="0.0"/>
                    <GradientStop Color="#EEE" Offset="1.0"/>
                </GradientStopCollection>
            </GradientBrush.GradientStops>
        </LinearGradientBrush>

        <LinearGradientBrush x:Key="HorizontalLightBrush" StartPoint="0,0" EndPoint="1,0">
            <GradientBrush.GradientStops>
                <GradientStopCollection>
                    <GradientStop Color="#FFF" Offset="0.0"/>
                    <GradientStop Color="#EEE" Offset="1.0"/>
                </GradientStopCollection>
            </GradientBrush.GradientStops>
        </LinearGradientBrush>

        <LinearGradientBrush x:Key="DarkBrush" StartPoint="0,0" EndPoint="0,1">
            <GradientBrush.GradientStops>
                <GradientStopCollection>
                    <GradientStop Color="#FFF" Offset="0.0"/>
                    <GradientStop Color="#AAA" Offset="1.0"/>
                </GradientStopCollection>
            </GradientBrush.GradientStops>
        </LinearGradientBrush>

        <LinearGradientBrush x:Key="PressedBrush" StartPoint="0,0" EndPoint="0,1">
            <GradientBrush.GradientStops>
                <GradientStopCollection>
                    <GradientStop Color="#BBB" Offset="0.0"/>
                    <GradientStop Color="#EEE" Offset="0.1"/>
                    <GradientStop Color="#EEE" Offset="0.9"/>
                    <GradientStop Color="#FFF" Offset="1.0"/>
                </GradientStopCollection>
            </GradientBrush.GradientStops>
        </LinearGradientBrush>

        <SolidColorBrush x:Key="DisabledForegroundBrush" Color="#888" />

        <SolidColorBrush x:Key="DisabledBackgroundBrush" Color="#EEE" />

        <SolidColorBrush x:Key="WindowBackgroundBrush" Color="#FFF" />

        <SolidColorBrush x:Key="SelectedBackgroundBrush" Color="#DDD" />

        <!-- Border Brushes -->

        <LinearGradientBrush x:Key="NormalBorderBrush" StartPoint="0,0" EndPoint="0,1">
            <GradientBrush.GradientStops>
                <GradientStopCollection>
                    <GradientStop Color="#CCC" Offset="0.0"/>
                    <GradientStop Color="#444" Offset="1.0"/>
                </GradientStopCollection>
            </GradientBrush.GradientStops>
        </LinearGradientBrush>

        <LinearGradientBrush x:Key="HorizontalNormalBorderBrush" StartPoint="0,0" EndPoint="1,0">
            <GradientBrush.GradientStops>
                <GradientStopCollection>
                    <GradientStop Color="#CCC" Offset="0.0"/>
                    <GradientStop Color="#444" Offset="1.0"/>
                </GradientStopCollection>
            </GradientBrush.GradientStops>
        </LinearGradientBrush>

        <LinearGradientBrush x:Key="DefaultedBorderBrush" StartPoint="0,0" EndPoint="0,1">
            <GradientBrush.GradientStops>
                <GradientStopCollection>
                    <GradientStop Color="#777" Offset="0.0"/>
                    <GradientStop Color="#000" Offset="1.0"/>
                </GradientStopCollection>
            </GradientBrush.GradientStops>
        </LinearGradientBrush>

        <LinearGradientBrush x:Key="PressedBorderBrush" StartPoint="0,0" EndPoint="0,1">
            <GradientBrush.GradientStops>
                <GradientStopCollection>
                    <GradientStop Color="#444" Offset="0.0"/>
                    <GradientStop Color="#888" Offset="1.0"/>
                </GradientStopCollection>
            </GradientBrush.GradientStops>
        </LinearGradientBrush>

        <SolidColorBrush x:Key="DisabledBorderBrush" Color="#AAA" />

        <SolidColorBrush x:Key="SolidBorderBrush" Color="#888" />

        <SolidColorBrush x:Key="LightBorderBrush" Color="#AAA" />

        <!-- Miscellaneous Brushes -->
        <SolidColorBrush x:Key="GlyphBrush" Color="#444" />

        <SolidColorBrush x:Key="LightColorBrush" Color="#DDD" />

        <ControlTemplate x:Key="ComboBoxToggleButton" TargetType="ToggleButton">
            <Grid>
                <Grid.ColumnDefinitions>
                    <ColumnDefinition />
                    <ColumnDefinition Width="20" />
                </Grid.ColumnDefinitions>
                <Border
      x:Name="Border" 
      Grid.ColumnSpan="2"
      CornerRadius="2"
      Background="{StaticResource NormalBrush}"
      BorderBrush="{StaticResource NormalBorderBrush}"
      BorderThickness="1" />
                <Border 
      Grid.Column="0"
      CornerRadius="2,0,0,2" 
      Margin="1" 
      Background="{StaticResource WindowBackgroundBrush}" 
      BorderBrush="{StaticResource NormalBorderBrush}"
      BorderThickness="0,0,1,0" />
                <Path 
      x:Name="Arrow"
      Grid.Column="1"     
      Fill="{StaticResource GlyphBrush}"
      HorizontalAlignment="Center"
      VerticalAlignment="Center"
      Data="M 0 0 L 4 4 L 8 0 Z"/>
            </Grid>
            <ControlTemplate.Triggers>
                <!--<Trigger Property="ToggleButton.IsMouseOver" Value="true">
                    <Setter TargetName="Border" Property="Background" Value="{StaticResource DarkBrush}" />
                </Trigger>-->
                <Trigger Property="ToggleButton.IsChecked" Value="true">
                    <Setter TargetName="Border" Property="Background" Value="{StaticResource PressedBrush}" />
                </Trigger>
                <Trigger Property="IsEnabled" Value="False">
                    <Setter TargetName="Border" Property="Background" Value="{StaticResource DisabledBackgroundBrush}" />
                    <Setter TargetName="Border" Property="BorderBrush" Value="{StaticResource DisabledBorderBrush}" />
                    <Setter Property="Foreground" Value="{StaticResource DisabledForegroundBrush}"/>
                    <Setter TargetName="Arrow" Property="Fill" Value="{StaticResource DisabledForegroundBrush}" />
                </Trigger>
            </ControlTemplate.Triggers>
        </ControlTemplate>

        <ControlTemplate x:Key="ComboBoxTextBox" TargetType="TextBox">
            <Border x:Name="PART_ContentHost" Focusable="False" Background="{TemplateBinding Background}" />
        </ControlTemplate>

        <Style x:Key="{x:Type ComboBox}" TargetType="ComboBox">
            <Setter Property="SnapsToDevicePixels" Value="true"/>
            <Setter Property="OverridesDefaultStyle" Value="true"/>
            <Setter Property="ScrollViewer.HorizontalScrollBarVisibility" Value="Auto"/>
            <Setter Property="ScrollViewer.VerticalScrollBarVisibility" Value="Auto"/>
            <Setter Property="ScrollViewer.CanContentScroll" Value="true"/>
            <Setter Property="MinWidth" Value="120"/>
            <Setter Property="MinHeight" Value="20"/>
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="ComboBox">
                        <Grid>
                            <ToggleButton 
            Name="ToggleButton" 
            Template="{StaticResource ComboBoxToggleButton}" 
            Grid.Column="2" 
            Focusable="false"
            IsChecked="{Binding Path=IsDropDownOpen,Mode=TwoWay,RelativeSource={RelativeSource TemplatedParent}}"
            ClickMode="Press">
                            </ToggleButton>
                            <ContentPresenter
            Name="ContentSite"
            IsHitTestVisible="False" 
            Content="{TemplateBinding SelectionBoxItem}"
            ContentTemplate="{TemplateBinding SelectionBoxItemTemplate}"
            ContentTemplateSelector="{TemplateBinding ItemTemplateSelector}"
            Margin="3,3,23,3"
            VerticalAlignment="Center"
            HorizontalAlignment="Left" />
                            <TextBox x:Name="PART_EditableTextBox"
            Style="{x:Null}" 
            Template="{StaticResource ComboBoxTextBox}" 
            HorizontalAlignment="Left" 
            VerticalAlignment="Center" 
            Margin="3,3,23,3"
            Focusable="True" 
            Background="Transparent"
            Visibility="Hidden"
            IsReadOnly="{TemplateBinding IsReadOnly}"/>
                            <Popup 
            Name="Popup"
            Placement="Bottom"
            IsOpen="{TemplateBinding IsDropDownOpen}"
            AllowsTransparency="True" 
            Focusable="False"
            PopupAnimation="Slide">
                                <Grid 
              Name="DropDown"
              SnapsToDevicePixels="True"                
              MinWidth="{TemplateBinding ActualWidth}"
              MaxHeight="{TemplateBinding MaxDropDownHeight}">
                                    <Border 
                x:Name="DropDownBorder"
                Background="{StaticResource WindowBackgroundBrush}"
                BorderThickness="1"
                BorderBrush="{StaticResource SolidBorderBrush}"/>
                                    <ScrollViewer Margin="4,6,4,6" SnapsToDevicePixels="True">
                                        <StackPanel IsItemsHost="True" KeyboardNavigation.DirectionalNavigation="Contained" />
                                    </ScrollViewer>
                                </Grid>
                            </Popup>
                        </Grid>
                        <ControlTemplate.Triggers>
                            <Trigger Property="HasItems" Value="false">
                                <Setter TargetName="DropDownBorder" Property="MinHeight" Value="95"/>
                            </Trigger>
                            <Trigger Property="IsEnabled" Value="false">
                                <Setter Property="Foreground" Value="{StaticResource DisabledForegroundBrush}"/>
                            </Trigger>
                            <Trigger Property="IsGrouping" Value="true">
                                <Setter Property="ScrollViewer.CanContentScroll" Value="false"/>
                            </Trigger>
                            <Trigger SourceName="Popup" Property="Popup.AllowsTransparency" Value="true">
                                <Setter TargetName="DropDownBorder" Property="CornerRadius" Value="4"/>
                                <Setter TargetName="DropDownBorder" Property="Margin" Value="0,2,0,0"/>
                            </Trigger>
                            <Trigger Property="IsEditable"
               Value="true">
                                <Setter Property="IsTabStop" Value="false"/>
                                <Setter TargetName="PART_EditableTextBox" Property="Visibility"    Value="Visible"/>
                                <Setter TargetName="ContentSite" Property="Visibility" Value="Hidden"/>
                            </Trigger>
                        </ControlTemplate.Triggers>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
            <Style.Triggers>
            </Style.Triggers>
        </Style>

    </Window.Resources>