DirectoryCreator/Themes/DarkTheme.xaml

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
    <!-- Base Colors -->
    <SolidColorBrush x:Key="WindowBackground" Color="#1E1E1E" />
    <SolidColorBrush x:Key="WindowForeground" Color="#FFFFFF" />
    <SolidColorBrush x:Key="PrimaryBackground" Color="#2D2D2D" />
    <SolidColorBrush x:Key="SecondaryBackground" Color="#333333" />
    <SolidColorBrush x:Key="BorderBrush" Color="#404040" />
    <SolidColorBrush x:Key="ButtonBackground" Color="#3E3E3E" />
    <SolidColorBrush x:Key="ButtonBackgroundHover" Color="#4A4A4A" />
    <SolidColorBrush x:Key="TextBoxBackground" Color="#2D2D2D" />

    <!-- ScrollBar Colors -->
    <SolidColorBrush x:Key="ScrollBarBackground" Color="#2D2D2D" />
    <SolidColorBrush x:Key="ScrollBarBorder" Color="#404040" />
    <SolidColorBrush x:Key="ScrollBarThumb" Color="#505050" />
    <SolidColorBrush x:Key="ScrollBarThumbHover" Color="#606060" />
    <SolidColorBrush x:Key="ScrollBarThumbPressed" Color="#707070" />

    <!-- Base Control Styles -->
    <Style TargetType="Window">
        <Setter Property="Background" Value="{StaticResource WindowBackground}" />
        <Setter Property="Foreground" Value="{StaticResource WindowForeground}" />
    </Style>

    <Style TargetType="Grid">
        <Setter Property="Background" Value="{StaticResource WindowBackground}" />
    </Style>

    <Style TargetType="Border">
        <Setter Property="Background" Value="{StaticResource WindowBackground}" />
        <Setter Property="BorderBrush" Value="{StaticResource BorderBrush}" />
    </Style>

    <Style TargetType="Button">
        <Setter Property="Background" Value="{StaticResource ButtonBackground}" />
        <Setter Property="Foreground" Value="{StaticResource WindowForeground}" />
        <Setter Property="BorderBrush" Value="{StaticResource BorderBrush}" />
    </Style>

    <Style TargetType="TextBox">
        <Setter Property="Background" Value="{StaticResource TextBoxBackground}" />
        <Setter Property="Foreground" Value="{StaticResource WindowForeground}" />
        <Setter Property="BorderBrush" Value="{StaticResource BorderBrush}" />
    </Style>

    <Style TargetType="TextBlock">
        <Setter Property="Foreground" Value="{StaticResource WindowForeground}" />
    </Style>

    <Style TargetType="CheckBox">
        <Setter Property="Foreground" Value="{StaticResource WindowForeground}" />
        <Setter Property="Background" Value="{StaticResource PrimaryBackground}" />
        <Setter Property="BorderBrush" Value="{StaticResource BorderBrush}" />
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="CheckBox">
                    <Grid x:Name="templateRoot" Background="Transparent" SnapsToDevicePixels="True">
                        <Grid.ColumnDefinitions>
                            <ColumnDefinition Width="Auto" />
                            <ColumnDefinition Width="*" />
                        </Grid.ColumnDefinitions>
                        <Border x:Name="checkBoxBorder" Background="{TemplateBinding Background}"
                                BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="1"
                                HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" Margin="1"
                                VerticalAlignment="{TemplateBinding VerticalContentAlignment}" Width="16" Height="16">
                            <Path x:Name="optionMark"
                                    Data="F1 M 9.97498,1.22334L 4.6983,9.09834L 4.52164,9.09834L 0,5.19331L 1.27664,3.52165L 4.255,6.08833L 8.33331,1.52588e-005L 9.97498,1.22334 Z"
                                    Fill="{StaticResource WindowForeground}" Margin="1" Opacity="0" Stretch="Uniform" />
                        </Border>
                        <ContentPresenter x:Name="contentPresenter" Grid.Column="1" Focusable="False"
                                HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}"
                                Margin="{TemplateBinding Padding}" RecognizesAccessKey="True"
                                SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"
                                VerticalAlignment="{TemplateBinding VerticalContentAlignment}" />
                    </Grid>
                    <ControlTemplate.Triggers>
                        <Trigger Property="IsChecked" Value="true">
                            <Setter Property="Opacity" TargetName="optionMark" Value="1" />
                        </Trigger>
                        <Trigger Property="IsMouseOver" Value="true">
                            <Setter Property="Background" TargetName="checkBoxBorder"
                                    Value="{StaticResource ButtonBackground}" />
                        </Trigger>
                        <Trigger Property="IsPressed" Value="true">
                            <Setter Property="Background" TargetName="checkBoxBorder"
                                    Value="{StaticResource ButtonBackgroundHover}" />
                        </Trigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>

    <!-- ComboBox Style -->
    <Style TargetType="ComboBox">
        <Setter Property="Background" Value="{StaticResource PrimaryBackground}" />
        <Setter Property="Foreground" Value="{StaticResource WindowForeground}" />
        <Setter Property="BorderBrush" Value="{StaticResource BorderBrush}" />
        <Style.Resources>
            <SolidColorBrush x:Key="{x:Static SystemColors.WindowBrushKey}" Color="#2D2D2D"/>
            <SolidColorBrush x:Key="{x:Static SystemColors.HighlightBrushKey}" Color="#404040"/>
            <SolidColorBrush x:Key="{x:Static SystemColors.ControlTextBrushKey}" Color="White"/>
            <SolidColorBrush x:Key="{x:Static SystemColors.HighlightTextBrushKey}" Color="White"/>
            <SolidColorBrush x:Key="{x:Static SystemColors.WindowTextBrushKey}" Color="White"/>
        </Style.Resources>
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="ComboBox">
                    <Grid>
                        <Border x:Name="border" Background="{TemplateBinding Background}"
                                BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="1">
                            <Grid>
                                <Grid.ColumnDefinitions>
                                    <ColumnDefinition Width="*" />
                                    <ColumnDefinition Width="Auto" />
                                </Grid.ColumnDefinitions>
                                <TextBlock
                                        Text="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=SelectionBoxItem.Description}"
                                        Margin="5,2" VerticalAlignment="Center" />
                                <ToggleButton x:Name="toggleButton" Grid.Column="1" Width="20"
                                        IsChecked="{Binding Path=IsDropDownOpen, Mode=TwoWay, RelativeSource={RelativeSource TemplatedParent}}"
                                        Background="Transparent" BorderThickness="0">
                                    <Path Data="M0,0 L3,4 L6,0" Fill="{StaticResource WindowForeground}"
                                            Stretch="Uniform" />
                                </ToggleButton>
                            </Grid>
                        </Border>
                        <Popup IsOpen="{TemplateBinding IsDropDownOpen}" Placement="Bottom"
                                PlacementTarget="{Binding ElementName=border}" PopupAnimation="Slide">
                            <Border Background="{StaticResource PrimaryBackground}"
                                    BorderBrush="{StaticResource BorderBrush}" BorderThickness="1">
                                <ScrollViewer MaxHeight="{TemplateBinding MaxDropDownHeight}"
                                        Background="{StaticResource PrimaryBackground}">
                                    <ItemsPresenter />
                                </ScrollViewer>
                            </Border>
                        </Popup>
                    </Grid>
                    <ControlTemplate.Triggers>
                        <Trigger Property="IsMouseOver" Value="True">
                            <Setter Property="Background" TargetName="border" Value="{StaticResource ButtonBackground}" />
                        </Trigger>
                        <Trigger Property="IsDropDownOpen" Value="True">
                            <Setter Property="Background" TargetName="border"
                                    Value="{StaticResource ButtonBackgroundHover}" />
                        </Trigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>

    <Style TargetType="ComboBoxItem">
        <Setter Property="Background" Value="Transparent" />
        <Setter Property="Foreground" Value="{StaticResource WindowForeground}" />
        <Setter Property="Height" Value="30" />
        <Setter Property="Margin" Value="0" />
        <Setter Property="Padding" Value="8,4" />
        <Style.Triggers>
            <Trigger Property="IsMouseOver" Value="True">
                <Setter Property="Background" Value="{StaticResource ButtonBackground}" />
            </Trigger>
            <Trigger Property="IsSelected" Value="True">
                <Setter Property="Background" Value="{StaticResource ButtonBackgroundHover}" />
            </Trigger>
        </Style.Triggers>
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="ComboBoxItem">
                    <Border x:Name="Bd" Background="{TemplateBinding Background}"
                            BorderBrush="{TemplateBinding BorderBrush}"
                            BorderThickness="{TemplateBinding BorderThickness}" Padding="{TemplateBinding Padding}">
                        <TextBlock Text="{Binding Description}" Margin="2" />
                    </Border>
                    <ControlTemplate.Triggers>
                        <Trigger Property="IsMouseOver" Value="True">
                            <Setter Property="Background" TargetName="Bd" Value="{StaticResource ButtonBackground}" />
                        </Trigger>
                        <Trigger Property="IsSelected" Value="True">
                            <Setter Property="Background" TargetName="Bd" Value="{StaticResource ButtonBackgroundHover}" />
                        </Trigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>

    <!-- ScrollBar Style -->
    <Style TargetType="ScrollBar">
        <Setter Property="Background" Value="{StaticResource ScrollBarBackground}" />
        <Setter Property="BorderBrush" Value="{StaticResource ScrollBarBorder}" />
    </Style>

    <Style TargetType="ScrollViewer">
        <Setter Property="Background" Value="{StaticResource WindowBackground}" />
        <Setter Property="BorderBrush" Value="{StaticResource BorderBrush}" />
        <Setter Property="Padding" Value="1" />
    </Style>

</ResourceDictionary>