presence/Presence.Desktop/Views/GroupView.axaml

<UserControl xmlns="https://github.com/avaloniaui"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:vm="using:Presence.Desktop.ViewModels"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        mc:Ignorable="d" d:DesignWidth="800" d:DesignHeight="450"
        x:Class="Presence.Desktop.Views.GroupView"
        x:DataType="vm:GroupViewModel">

    <Design.DataContext>
        <vm:GroupViewModel/>
    </Design.DataContext>
	
	<DockPanel Background="Black">
		
		<StackPanel DockPanel.Dock="Bottom">
			<TextBlock Text="List ↑" HorizontalAlignment="Center"/>
		</StackPanel>
		
		<StackPanel Spacing="10" HorizontalAlignment="Center" DockPanel.Dock="Top" Orientation="Horizontal">
			<Button Content="Назад" Command="{Binding GoBackCommand}"/>
			
			<TextBlock Text="Combobox ->"/>
			
			<ComboBox  ItemsSource="{Binding Groups}" SelectedValue="{Binding SelectedGroupItem}">
				<ComboBox.ItemTemplate>
					<DataTemplate>
						<TextBlock Text="{Binding Name}"/>
					</DataTemplate>
				</ComboBox.ItemTemplate>
			</ComboBox>
			
            <ComboBox ItemsSource="{Binding SecondComboBoxItems}" SelectedValue="{Binding SelectedSecondItem}">
                <ComboBox.ItemTemplate>
                    <DataTemplate>
                        <TextBlock Text="{Binding}"/>
                    </DataTemplate>
                </ComboBox.ItemTemplate>
            </ComboBox>
			
            <Button Content="Delete Users"
                    Command="{Binding DeleteUsersByGroupCommand}"/>
            <Button Content="Import Students" Command="{Binding ImportStudentsCommand}"/>
		</StackPanel>
		
		<Border>
			<ListBox Background="Black" ItemsSource="{Binding Users}" SelectedItem="{Binding SelectedUser}">
				<ListBox.ItemTemplate>
					<DataTemplate>
						<StackPanel Orientation="Horizontal">
							<TextBlock Text="{Binding Name}" />
						</StackPanel>
					</DataTemplate>
				</ListBox.ItemTemplate>
				
				<ListBox.ContextMenu>
					<ContextMenu>
						<MenuItem Header="Delete User"
								  Command="{Binding DeleteUserCommand}"
								  CommandParameter="{Binding SelectedUser}" />
						<MenuItem Header="Update FIO">
							
							<StackPanel>
								<TextBox Text="{Binding NewFIO, Mode=TwoWay}" Width="150" />
								<Button Content="Update"
										Command="{Binding UpdateUserFIOCommand}"
										CommandParameter="{Binding SelectedUser}" />
							</StackPanel>
						</MenuItem>
					</ContextMenu>
				</ListBox.ContextMenu>
			</ListBox>
		</Border>
	</DockPanel>
</UserControl>