<ComboBox Width="200" VerticalAlignment="Center" IsEditable="True">
    <ComboBoxItem Content="Item 1"/>
    <ComboBoxItem Content="Item 2"/>
    <ComboBoxItem Content="Item 3"/>
    <ComboBoxItem Content="Item 4"/>
    <ComboBoxItem Content="Item 5"/>
</ComboBox>

<UserControl x:Class="GeoSearchControl"
  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
  UseLayoutRounding="True"
  FontFamily="../Themes/Fonts/#Verdana"
  x:Name="control">

  <UserControl.Resources>

    <SolidColorBrush x:Key="ComboBoxNormalBorderBrush" Color="#2f2f37" />
    <SolidColorBrush x:Key="ComboBoxNormalBackgroundBrush" Color="#212125" />
    <SolidColorBrush x:Key="ComboBoxDisabledForegroundBrush" Color="#888" />
    <SolidColorBrush x:Key="ComboBoxDisabledBackgroundBrush" Color="#eee" />
    <SolidColorBrush x:Key="ComboBoxDisabledBorderBrush" Color="#888" />

    <ControlTemplate TargetType="ToggleButton" x:Key="ComboBoxToggleButtonTemplate">
      <Grid>
        <Grid.ColumnDefinitions>
          <ColumnDefinition />
          <ColumnDefinition Width="20" />
        </Grid.ColumnDefinitions>
        <Border Name="Border"
                BorderBrush="{StaticResource ComboBoxNormalBorderBrush}"
                CornerRadius="2" BorderThickness="0.5"
                Background="{StaticResource ComboBoxNormalBackgroundBrush}" />
        <Border Grid.Column="1" Margin="2,0,2,0" BorderBrush="#444" Name="ButtonBorder"
                CornerRadius="2" BorderThickness="0"
                Background="{StaticResource ComboBoxNormalBackgroundBrush}" />

        <Path Name="Arrow" Grid.Column="1"
              Data="M0,0 L0,2 L4,6 L8,2 L8,0 L4,4 z"
              HorizontalAlignment="Center" Fill="#999"
              VerticalAlignment="Center" />
      </Grid>
      <ControlTemplate.Triggers>
        <Trigger Property="UIElement.IsMouseOver" Value="True">
          <Setter Property="Background" TargetName="ButtonBorder" Value="#454550"/>
        </Trigger>
        <Trigger Property="ToggleButton.IsChecked" Value="True">
          <Setter Property="Background" TargetName="ButtonBorder" Value="#606070"/>
          <Setter Property="Shape.Fill" TargetName="Arrow" Value="#FF8D979E"/>
        </Trigger>
        <Trigger Property="UIElement.IsEnabled" Value="False">
          <Setter Property="Background" TargetName="Border" Value="{StaticResource ComboBoxDisabledBackgroundBrush}"/>
          <Setter Property="Background" TargetName="ButtonBorder" Value="{StaticResource ComboBoxDisabledBackgroundBrush}"/>
          <Setter Property="Border.BorderBrush" TargetName="ButtonBorder" Value="{StaticResource ComboBoxDisabledBorderBrush}"/>
          <Setter Property="TextElement.Foreground" Value="{StaticResource ComboBoxDisabledForegroundBrush}"/>
          <Setter Property="Shape.Fill" TargetName="Arrow" Value="#999"/>
        </Trigger>
      </ControlTemplate.Triggers>
    </ControlTemplate>

    <Style x:Key="ComboBoxFlatStyle"  TargetType="{x:Type ComboBox}">
      <Setter Property="SnapsToDevicePixels" Value="True"/>
      <Setter Property="FrameworkElement.OverridesDefaultStyle" Value="True"/>
      <Setter Property="ScrollViewer.HorizontalScrollBarVisibility" Value="Auto"/>
      <Setter Property="ScrollViewer.VerticalScrollBarVisibility" Value="Auto"/>
      <Setter Property="ScrollViewer.CanContentScroll" Value="True"/>
      <Setter Property="TextElement.Foreground" Value="#c0c0c0"/>
      <Setter Property="FrameworkElement.FocusVisualStyle" Value="{x:Null}"/>
      <Setter Property="Control.Template">
        <Setter.Value>
          <ControlTemplate TargetType="ComboBox">
            <Grid>

              <ToggleButton Name="ToggleButton"
                  ClickMode="Press" Focusable="False"
                  IsChecked="{Binding Path=IsDropDownOpen, RelativeSource={RelativeSource TemplatedParent}, Mode=TwoWay}"
                  Template="{StaticResource ComboBoxToggleButtonTemplate}"/>

              <ContentPresenter Name="ContentSite" Margin="3" IsHitTestVisible="False"
                                HorizontalAlignment="Left" VerticalAlignment="Center"
                                Content="{TemplateBinding ComboBox.SelectionBoxItem}"
                                ContentTemplate="{TemplateBinding ComboBox.SelectionBoxItemTemplate}"
                                ContentTemplateSelector="{TemplateBinding ItemTemplateSelector}"/>
              <TextBox Name="PART_EditableTextBox" Margin="3,3,23,3"
                       IsReadOnly="{TemplateBinding IsReadOnly}"
                       Visibility="Hidden" Background="Transparent"
                       HorizontalAlignment="Left" VerticalAlignment="Center"
                       Focusable="True" >
                <TextBox.Template>
                  <ControlTemplate TargetType="TextBox" >
                    <Border Name="PART_ContentHost" Focusable="False"/>
                  </ControlTemplate>
                </TextBox.Template>
              </TextBox>
              <Button Width="20" HorizontalAlignment="Right" Margin="2,2,23,2"/>
              <!-- Popup showing items -->
              <Popup Name="Popup" Placement="Bottom"
                     Focusable="False" AllowsTransparency="True"
                     IsOpen="{TemplateBinding ComboBox.IsDropDownOpen}"
                     PopupAnimation="Slide">
                <Grid Name="DropDown" SnapsToDevicePixels="True"
                      MinWidth="{TemplateBinding FrameworkElement.ActualWidth}"
                      MaxHeight="{TemplateBinding ComboBox.MaxDropDownHeight}">
                  <Border Name="DropDownBorder" Background="#353545" Margin="0,1,0,0"
                          BorderThickness="1" BorderBrush="#707075"/>
                  <ScrollViewer Margin="4" SnapsToDevicePixels="True">
                    <ItemsPresenter KeyboardNavigation.DirectionalNavigation="Contained" />
                  </ScrollViewer>
                </Grid>
              </Popup>
            </Grid>

            <ControlTemplate.Triggers>
              <Trigger Property="ItemsControl.HasItems" Value="False">
                <Setter Property="FrameworkElement.MinHeight" TargetName="DropDownBorder" Value="95"/>
              </Trigger>
              <Trigger Property="UIElement.IsEnabled" Value="False">
                <Setter Property="TextElement.Foreground" Value="{StaticResource ComboBoxDisabledForegroundBrush}"/>
              </Trigger>
              <Trigger Property="ComboBox.IsEditable" Value="True">
                <Setter Property="KeyboardNavigation.IsTabStop" Value="False"/>
                <Setter Property="UIElement.Visibility" TargetName="PART_EditableTextBox" Value="Visible"/>
                <Setter Property="UIElement.Visibility" TargetName="ContentSite" Value="Hidden"/>
              </Trigger>
            </ControlTemplate.Triggers>
          </ControlTemplate>
        </Setter.Value>
      </Setter>
    </Style>
  </UserControl.Resources>

  <UserControl.Style>

    <Style TargetType="{x:Type GeoSearchControl}">
      <Setter Property="Background" Value="Transparent" />
      <Setter Property="Padding" Value="2" />
      <Setter Property="SnapsToDevicePixels" Value="True" />

      <Setter Property="Template">
        <Setter.Value>
          <ControlTemplate TargetType="{x:Type GeoSearchControl}">
            <ComboBox Style="{StaticResource ComboBoxFlatStyle}" ItemsSource="{Binding ElementName=control, Path=SearchItems}" IsEditable="True"/>
          </ControlTemplate>
        </Setter.Value>
      </Setter>
    </Style>
  </UserControl.Style>

</UserControl>