Fix BackGround of ComboBox (#1748)

* Fix #1728. Move CornerRadius Element.

* fix BackGround of ComboBox

* fix conflict

Author: soi013

MaterialDesignThemes.Wpf/Themes/MaterialDesignTheme.ComboBox.xaml

@@ -55,8 +55,7 @@
                 </Border.Effect>
             </Border>
          <Border Margin="1"
-                    CornerRadius="{Binding Path=CornerRadius, RelativeSource={RelativeSource AncestorType=wpf:ComboBoxPopup}}"
-                    Background="{Binding ElementName=PART_Popup, Path=Background}">
+                 CornerRadius="{Binding Path=CornerRadius, RelativeSource={RelativeSource AncestorType=wpf:ComboBoxPopup}}" >
             <Grid SnapsToDevicePixels="True">
                <Grid.RowDefinitions>
                   <RowDefinition Height="Auto"/>
@@ -65,21 +64,21 @@
                   <RowDefinition Height="Auto"/>
                   <RowDefinition Height="Auto"/>
                </Grid.RowDefinitions>
-               <Border Grid.Row="0" Height="{StaticResource PopupTopBottomMargin}"/>
+               <Border Grid.Row="0" Height="{StaticResource PopupTopBottomMargin}" Background="{Binding ElementName=PART_Popup, Path=Background}"/>
                <ContentPresenter Grid.Row="1"/>
-               <Border Grid.Row="2" Height="{StaticResource PopupContentPresenterExtend}"/>
+               <Border Grid.Row="2" Height="{StaticResource PopupContentPresenterExtend}" Background="{Binding ElementName=PART_Popup, Path=Background}"/>
 
                <Grid Grid.Row="3">
                   <Grid.ColumnDefinitions>
                      <ColumnDefinition Width="Auto"/>
                      <ColumnDefinition Width="Auto"/>
                      <ColumnDefinition Width="*"/>
                   </Grid.ColumnDefinitions>
-                  <Border Grid.Column="0" Width="{StaticResource PopupLeftRightMargin}"/>
+                  <Border Grid.Column="0" Width="{StaticResource PopupLeftRightMargin}" Background="{Binding ElementName=PART_Popup, Path=Background}"/>
                   <Grid Grid.Column="1"
                              Width="{Binding RelativeSource={RelativeSource AncestorType={x:Type wpf:ComboBoxPopup}}, Path=VisiblePlacementWidth}"
                              Height="{Binding ElementName=templateRoot, Path=ActualHeight}"/>
-                  <Border Grid.Column="2" MinWidth="{StaticResource PopupLeftRightMargin}"/>
+                  <Border Grid.Column="2" MinWidth="{StaticResource PopupLeftRightMargin}" Background="{Binding ElementName=PART_Popup, Path=Background}"/>
                </Grid>
                <Border Grid.Row="4"  Height="{StaticResource PopupTopBottomMargin}"/>
             </Grid>
@@ -102,8 +101,7 @@
                 </Border.Effect>
             </Border>
             <Border Margin="1"
-                    CornerRadius="{Binding Path=CornerRadius, RelativeSource={RelativeSource AncestorType=wpf:ComboBoxPopup}}"
-                    Background="{Binding ElementName=PART_Popup, Path=Background}">
+                    CornerRadius="{Binding Path=CornerRadius, RelativeSource={RelativeSource AncestorType=wpf:ComboBoxPopup}}">
                <Grid SnapsToDevicePixels="True">
                 <Grid.RowDefinitions>
                     <RowDefinition Height="Auto"/>
@@ -113,28 +111,33 @@
                     <RowDefinition Height="Auto"/>
                 </Grid.RowDefinitions>
                 <Border Grid.Row="0"
-                        Height="{StaticResource PopupTopBottomMargin}"/>
+                        Height="{StaticResource PopupTopBottomMargin}"
+                        Background="{Binding ElementName=PART_Popup, Path=Background}"/>
                 <Grid Grid.Row="1">
                     <Grid.ColumnDefinitions>
                         <ColumnDefinition Width="Auto"/>
                         <ColumnDefinition Width="Auto"/>
                         <ColumnDefinition Width="*"/>
                     </Grid.ColumnDefinitions>
-                    <Border Grid.Column="0"
+                     <Border Grid.Column="0"
+                            Background="{Binding ElementName=PART_Popup, Path=Background}"
                             Width="{StaticResource PopupLeftRightMargin}"/>
                     <Grid Grid.Column="1"
                           Width="{Binding RelativeSource={RelativeSource AncestorType={x:Type wpf:ComboBoxPopup}}, Path=VisiblePlacementWidth}"
                           Height="{Binding ElementName=templateRoot, Path=ActualHeight}"/>
                     <Border Grid.Column="2"
+                            Background="{Binding ElementName=PART_Popup, Path=Background}"
                             MinWidth="{StaticResource PopupLeftRightMargin}"/>
                 </Grid>
 
                 <Border Grid.Row="2"
+                        Background="{Binding ElementName=PART_Popup, Path=Background}"
                         Height="{StaticResource PopupContentPresenterExtend}"/>
 
                 <ContentPresenter Grid.Row="3"/>
 
                 <Border Grid.Row="4"
+                        Background="{Binding ElementName=PART_Popup, Path=Background}"
                         Height="{StaticResource PopupTopBottomMargin}" />
              </Grid>
           </Border>
@@ -164,9 +167,13 @@
                     <RowDefinition Height="*"/>
                     <RowDefinition Height="Auto"/>
                 </Grid.RowDefinitions>
-                <Border Grid.Row="0" Height="{StaticResource PopupTopBottomMargin}"/>
+                <Border Grid.Row="0" 
+                        Height="{StaticResource PopupTopBottomMargin}"
+                        Background="{Binding ElementName=PART_Popup, Path=Background}" />
                 <ContentPresenter Grid.Row="1"/>
-                <Border Grid.Row="2" Height="{StaticResource PopupTopBottomMargin}" />
+                <Border Grid.Row="2"
+                        Height="{StaticResource PopupTopBottomMargin}"
+                        Background="{Binding ElementName=PART_Popup, Path=Background}" />
             </Grid>
          </Border>
       </Grid>