MainWindow.xaml

<dx:ThemedWindow x:Class="DXApplication14.MainWindow"
                 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"
                 xmlns:dxmvvm="http://schemas.devexpress.com/winfx/2008/xaml/mvvm"
                 xmlns:dxsch="http://schemas.devexpress.com/winfx/2008/xaml/scheduling"
                 xmlns:local="clr-namespace:DXApplication14"
                 Width="1000" 
                 Height="800"
                 Title="MainWindow">

    <dx:ThemedWindow.DataContext>
        <local:MainViewModel/>
    </dx:ThemedWindow.DataContext>

    <DockPanel>
        <dxb:MainMenuControl DockPanel.Dock="Top">
            <dxb:BarButtonItem Content="Add a regular appointment">
                <dxmvvm:Interaction.Behaviors>
                    <dxmvvm:CompositeCommandBehavior CanExecuteCondition="AnyCommandCanBeExecuted">
                        <dxmvvm:CommandItem Command="{Binding AddApptCommand}"
                                            CommandParameter="false" />
                        <dxmvvm:CommandItem CheckCanExecute="False"
                                            Command="{Binding ElementName=scheduler,
                                                              Path=Commands.ShowAppointmentWindowCommand}" />
                    </dxmvvm:CompositeCommandBehavior>
                </dxmvvm:Interaction.Behaviors>
            </dxb:BarButtonItem>
            <dxb:BarButtonItem Content="Add a recurrent appointment">
                <dxmvvm:Interaction.Behaviors>
                    <dxmvvm:CompositeCommandBehavior CanExecuteCondition="AnyCommandCanBeExecuted">
                        <dxmvvm:CommandItem Command="{Binding AddApptCommand}"
                                            CommandParameter="True" />
                        <dxmvvm:CommandItem CheckCanExecute="False"
                                            Command="{Binding ElementName=scheduler, 
                                                              Path=Commands.ShowAppointmentWindowCommand}" />
                    </dxmvvm:CompositeCommandBehavior>
                </dxmvvm:Interaction.Behaviors>
            </dxb:BarButtonItem>
        </dxb:MainMenuControl>
        <dxsch:SchedulerControl x:Name="scheduler"
                                SelectedAppointmentsSource="{Binding SelectedAppointments}"
                                SelectedInterval="{Binding Interval, Mode=TwoWay}">
            <dxsch:SchedulerControl.DataSource>
                <dxsch:DataSource AppointmentsSource="{Binding Appointments}">
                    <dxsch:DataSource.AppointmentMappings>
                        <dxsch:AppointmentMappings Description="Description"
                                                   End="End"
                                                   RecurrenceInfo="RecurrenceInfo"
                                                   Start="Start"
                                                   Subject="Subject"
                                                   Type="Type" />
                    </dxsch:DataSource.AppointmentMappings>
                </dxsch:DataSource>
            </dxsch:SchedulerControl.DataSource>
        </dxsch:SchedulerControl>
    </DockPanel>

</dx:ThemedWindow>