<Window
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:FlyoutExample"
        xmlns:dxe="http://schemas.devexpress.com/winfx/2008/xaml/editors"
        xmlns:dx="http://schemas.devexpress.com/winfx/2008/xaml/core"
        x:Class="FlyoutExample.MainWindow"
        Title="MainWindow" Height="350" Width="525">
    <Window.Resources>
        <Style x:Key="Top" TargetType="dxe:FlyoutControl">
            <Setter Property="Settings">
                <Setter.Value>
                    <dxe:FlyInSettings/>
                </Setter.Value>
            </Setter>
            <Setter Property="HorizontalAlignment" Value="Stretch"/>
            <Setter Property="VerticalAlignment" Value="Top"/>
        </Style>
        <Style x:Key="Button" TargetType="dxe:FlyoutControl">
            <Setter Property="Settings">
                <Setter.Value>
                    <dxe:FlyoutSettings ShowIndicator="True" 
                                        Placement="Top" 
                                        IndicatorHorizontalAlignment="Right"/>
                </Setter.Value>
            </Setter>
        </Style>
    </Window.Resources>
    <Grid x:Name="LayoutRoot">
        <dxe:FlyoutControl x:Name="flyoutControl"
                           FontSize="16"
                           AllowMoveAnimation="False"
                           FontFamily="Segoe UI Light"/>
        <Grid>
            <Grid.ColumnDefinitions>
                <ColumnDefinition/>
                <ColumnDefinition/>
            </Grid.ColumnDefinitions>
            <dx:SimpleButton Grid.Column="0"  
                             Content="Open flyout 1" 
                             Height="30" 
                             VerticalAlignment="Center" 
                             HorizontalAlignment="Center" 
                             Click="OpenFlyout"/>
            <dx:SimpleButton Grid.Column="1"  
                             Content="Open flyout 2" 
                             Height="30" 
                             VerticalAlignment="Center" 
                             HorizontalAlignment="Center" 
                             Click="OpenInnerFlyout"/>
        </Grid>
    </Grid>
</Window>

using System.Windows;

namespace FlyoutExample {
    public partial class MainWindow : Window {
        public MainWindow() {
            InitializeComponent();
        }
        void OpenInnerFlyout(object sender, RoutedEventArgs e) {
            flyoutControl.PlacementTarget = LayoutRoot;
            flyoutControl.Content = "My target is " + LayoutRoot.GetType().ToString();
            flyoutControl.Style = Resources["Top"] as Style; 
            flyoutControl.IsOpen = true;
        }
        void OpenFlyout(object sender, RoutedEventArgs e) {
            flyoutControl.PlacementTarget = sender as FrameworkElement;
            flyoutControl.Content = "My target is " + flyoutControl.PlacementTarget.GetType().ToString();
            flyoutControl.Style = Resources["Button"] as Style;
            flyoutControl.IsOpen = true;
        }
    }
}

Imports System.Windows

Namespace FlyoutExample
    Public Partial Class MainWindow
        Inherits Window

        Public Sub New()
            InitializeComponent()
        End Sub

        Private Sub OpenInnerFlyout(ByVal sender As Object, ByVal e As RoutedEventArgs)
            flyoutControl.PlacementTarget = LayoutRoot
            flyoutControl.Content = "My target is " & LayoutRoot.GetType.ToString()
            flyoutControl.Style = TryCast(Resources("Top"), Style)
            flyoutControl.IsOpen = True
        End Sub

        Private Sub OpenFlyout(ByVal sender As Object, ByVal e As RoutedEventArgs)
            flyoutControl.PlacementTarget = TryCast(sender, FrameworkElement)
            flyoutControl.Content = "My target is " & flyoutControl.PlacementTarget.GetType.ToString()
            flyoutControl.Style = TryCast(Resources("Button"), Style)
            flyoutControl.IsOpen = True
        End Sub
    End Class
End Namespace