SplitButtonAdv
├── Primary Button (default action)
│   ├── Label (text)
│   ├── Icon (SmallIcon/LargeIcon/IconTemplate)
│   └── Command (ICommand binding)
└── Dropdown Arrow (opens menu)
    └── DropDownMenuGroup (container)
        ├── DropDownMenuItem (standard items)
        │   ├── Header (text)
        │   ├── Icon (image)
        │   ├── IsCheckable (checkbox support)
        │   └── Command (ICommand binding)
        └── MoreItems (custom UIElement items)

<Window xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:syncfusion="http://schemas.syncfusion.com/wpf">
    <Grid>
        <syncfusion:SplitButtonAdv Label="Colors" 
                                    SizeMode="Normal" 
                                    Click="SplitButton_Click">
            <syncfusion:DropDownMenuGroup>
                <syncfusion:DropDownMenuItem Header="Red" 
                                             Click="MenuItem_Click"/>
                <syncfusion:DropDownMenuItem Header="Green" 
                                             Click="MenuItem_Click"/>
                <syncfusion:DropDownMenuItem Header="Blue" 
                                             Click="MenuItem_Click"/>
            </syncfusion:DropDownMenuGroup>
        </syncfusion:SplitButtonAdv>
    </Grid>
</Window>

using Syncfusion.Windows.Tools.Controls;

private void SplitButton_Click(object sender, RoutedEventArgs e)
{
    MessageBox.Show("Primary action executed");
}

private void MenuItem_Click(object sender, RoutedEventArgs e)
{
    var menuItem = sender as DropDownMenuItem;
    MessageBox.Show($"Selected: {menuItem.Header}");
}

<syncfusion:SplitButtonAdv Label="Country" SizeMode="Normal">
    <syncfusion:DropDownMenuGroup ItemsSource="{Binding Countries}">
        <syncfusion:DropDownMenuGroup.ItemTemplate>
            <DataTemplate>
                <syncfusion:DropDownMenuItem 
                    Header="{Binding Name}"
                    Command="{Binding DataContext.SelectCountryCommand, 
                             RelativeSource={RelativeSource AncestorType=syncfusion:SplitButtonAdv}}"
                    CommandParameter="{Binding}">
                    <syncfusion:DropDownMenuItem.Icon>
                        <Image Source="{Binding FlagIcon}"/>
                    </syncfusion:DropDownMenuItem.Icon>
                </syncfusion:DropDownMenuItem>
            </DataTemplate>
        </syncfusion:DropDownMenuGroup.ItemTemplate>
    </syncfusion:DropDownMenuGroup>
</syncfusion:SplitButtonAdv>

public class ViewModel : NotificationObject
{
    private bool _canPerformAction = true;
    
    public DelegateCommand<object> ClickCommand { get; set; }
    
    public bool CanPerformAction
    {
        get => _canPerformAction;
        set
        {
            _canPerformAction = value;
            ClickCommand.RaiseCanExecuteChanged();
            RaisePropertyChanged(nameof(CanPerformAction));
        }
    }
    
    public ViewModel()
    {
        ClickCommand = new DelegateCommand<object>(
            ExecuteAction, 
            CanExecuteAction);
    }
    
    private bool CanExecuteAction(object parameter) => CanPerformAction;
    
    private void ExecuteAction(object parameter)
    {
        MessageBox.Show($"Action executed: {parameter}");
    }
}

<syncfusion:SplitButtonAdv Label="Action" 
                            Command="{Binding ClickCommand}"
                            CommandParameter="Primary Action">
    <!-- Dropdown items -->
</syncfusion:SplitButtonAdv>

<Window.Resources>
    <DataTemplate x:Key="customIconTemplate">
        <Grid Width="32" Height="32">
            <Path Data="M10,0 L20,10 L10,20 L0,10 Z" 
                  Fill="#FF3A3A38" 
                  Stretch="Fill"/>
        </Grid>
    </DataTemplate>
</Window.Resources>

<syncfusion:SplitButtonAdv Label="Custom Icon" 
                            SizeMode="Large"
                            IconTemplate="{StaticResource customIconTemplate}">
    <!-- Dropdown items -->
</syncfusion:SplitButtonAdv>

<syncfusion:SplitButtonAdv Label="Options" SizeMode="Normal">
    <syncfusion:DropDownMenuGroup MaxHeight="200" 
                                    ScrollBarVisibility="Visible"
                                    IconBarEnabled="True">
        <syncfusion:DropDownMenuItem Header="Option 1" 
                                     IsCheckable="True" 
                                     IsChecked="True"/>
        <syncfusion:DropDownMenuItem Header="Option 2" 
                                     IsCheckable="True"/>
        <syncfusion:DropDownMenuItem Header="Option 3" 
                                     IsCheckable="True"/>
        <!-- More items... -->
    </syncfusion:DropDownMenuGroup>
</syncfusion:SplitButtonAdv>