public class BarManagerCategory :
    DependencyObject

Public Class BarManagerCategory
    Inherits DependencyObject

Imports System
Imports System.Collections.Generic
Imports System.Configuration
Imports System.Data
Imports System.Linq
Imports System.Windows

Namespace WpfApplication3
    ''' <summary>
    ''' Interaction logic for App.xaml
    ''' </summary>
    Partial Public Class App
        Inherits Application

        Private Sub OnAppStartup_UpdateThemeName(ByVal sender As Object, ByVal e As StartupEventArgs)

            DevExpress.Xpf.Core.ApplicationThemeHelper.UpdateApplicationThemeName()
        End Sub
    End Class
End Namespace

<Window x:Class="WpfApplication3.Window1" 
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:dx="http://schemas.devexpress.com/winfx/2008/xaml/core" 
        xmlns:dxb="http://schemas.devexpress.com/winfx/2008/xaml/bars"
        Title="Window1" Height="300" Width="300" >
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto" />
            <RowDefinition Height="*"/>
        </Grid.RowDefinitions>

        <dxb:BarContainerControl Grid.Row="0">
            <dxb:ToolBarControl Caption="Main Toolbar">
                <dxb:BarCheckItem Content="Bold" Glyph="{dx:DXImage Image=Bold_16x16.png}" CategoryName="Format" 
                                  CheckedChanged="checkBtnBold_CheckChanged"/>
                <dxb:BarCheckItem Content="Italic" Glyph="{dx:DXImage Image=Italic_16x16.png}" CategoryName="Format" 
                                  CheckedChanged="checkBtnItalic_CheckChanged"/>
            </dxb:ToolBarControl>
        </dxb:BarContainerControl>
    </Grid>
</Window>

<Application x:Class="WpfApplication3.App" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" StartupUri="Window1.xaml" Startup="OnAppStartup_UpdateThemeName">
    <Application.Resources>

    </Application.Resources>
</Application>

Imports System
Imports System.Collections.Generic
Imports System.Linq
Imports System.Text
Imports System.Windows
Imports System.Windows.Controls
Imports System.Windows.Data
Imports System.Windows.Documents
Imports System.Windows.Input
Imports System.Windows.Media
Imports System.Windows.Media.Imaging
Imports System.Windows.Navigation
Imports System.Windows.Shapes
Imports DevExpress.Xpf.Bars

Namespace WpfApplication3
    ''' <summary>
    ''' Interaction logic for Window1.xaml
    ''' </summary>
    Partial Public Class Window1
        Inherits Window

        Public Sub New()
            InitializeComponent()
        End Sub

        Private Sub checkBtnItalic_CheckChanged(ByVal sender As Object, ByVal e As ItemClickEventArgs)
            '...
        End Sub

        Private Sub checkBtnBold_CheckChanged(ByVal sender As Object, ByVal e As DevExpress.Xpf.Bars.ItemClickEventArgs)
            '...
        End Sub
    End Class
End Namespace

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using DevExpress.Xpf.Bars;

namespace WpfApplication3 {
    /// <summary>
    /// Interaction logic for Window1.xaml
    /// </summary>
    public partial class Window1 : Window {
        public Window1() {
            InitializeComponent();
        }

        void checkBtnItalic_CheckChanged(object sender, ItemClickEventArgs e) {
            //...
        }

        void checkBtnBold_CheckChanged(object sender, DevExpress.Xpf.Bars.ItemClickEventArgs e) {
            //...
        }
    }
}