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="Azure">
        <Button Content="Назад" Command="{Binding GoBackCommand}" Foreground="Black" DockPanel.Dock="Top" HorizontalAlignment="Left" VerticalAlignment="Top" Margin="10" />
        <StackPanel Width="200" DockPanel.Dock="Right" HorizontalAlignment="Center" Background="Gray">
            <Button Content="Remove Users by Group" HorizontalAlignment="Center" Margin="10" Command="{Binding ButtonRemoveUsersByGroup}"/>
            <Button Content="Import Students" HorizontalAlignment="Center" Margin="10" Command="{Binding ImportStudentsCommand}"/>
        </StackPanel>

        <StackPanel DockPanel.Dock="Bottom">
            <TextBlock Text="List ↑" HorizontalAlignment="Center"/>
        </StackPanel>

        <StackPanel Spacing="10" HorizontalAlignment="Center" DockPanel.Dock="Top" Orientation="Horizontal">
            <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>
            <ComboBox/>
        </StackPanel>

        <Border>
            <ListBox Background="Bisque"
                     ItemsSource="{Binding Users}"
                     SelectedItems="{Binding SelectedUsers}"
                     SelectionMode="Multiple">
                <ListBox.ItemTemplate>
                    <DataTemplate>
                        <StackPanel Orientation="Horizontal" Margin="5">
                            <TextBlock Text="{Binding Name}" Foreground="Black" />
                        </StackPanel>
                    </DataTemplate>
                </ListBox.ItemTemplate>

                <ListBox.ContextMenu>
                    <ContextMenu>
                        <MenuItem Header="Delete User"
                                Command="{Binding RemoveSelectedUsersCommand}"
                                CommandParameter="{Binding SelectedUsers}" />
                        <MenuItem Header="Update FIO">
                            <StackPanel>
                                <TextBox Text="{Binding NewFIO, Mode=TwoWay}" Width="150" />
                                <Button Content="Update"
                                        Command="{Binding UpdateUserFIOCommand}"
                                        CommandParameter="{Binding SelectedUserForUpdate}" />
                            </StackPanel>
                        </MenuItem>
                    </ContextMenu>
                </ListBox.ContextMenu>
            </ListBox>
        </Border>
    </DockPanel>
</UserControl>