Закрытие UserControl при нажатии на кнопку

Есть форма, на которой при нажатии на кнопку "x:Name="StartChatWithUser_btn"" происходит вызов UserControl окна, и стоит дилемма, как закрыть UserControl при нажатии на кнопку "x:Name="Return_btn"".

XAML первой формы:

 <StackPanel x:Name="WindowChat" Grid.RowSpan="3" Background="White" Width="400" Height="630" Initialized="WindowChat_Initialized"  >
            <StackPanel.Effect>
                <DropShadowEffect BlurRadius="30" ShadowDepth="5" Color="#FFACACAC"/>
            </StackPanel.Effect>
            <Grid Height="80" Background="White">
                <Grid.Effect>
                    <DropShadowEffect BlurRadius="30" ShadowDepth="5" Color="#FFACACAC"/>
                </Grid.Effect>
                <Grid.ColumnDefinitions>
                    <ColumnDefinition Width="auto"/>
                    <ColumnDefinition Width="3*"/>
                    <ColumnDefinition Width="auto"/>
                </Grid.ColumnDefinitions>
                <TextBlock Text="Чат" Grid.Column="0" HorizontalAlignment="Center" FontSize="25" 
                           VerticalAlignment="Center" Margin="10"/>
                <Button Grid.Column="2" Style="{StaticResource MaterialDesignFloatingActionMiniAccentButton}" 
                        Width="25" Height="25" Padding="0" Background="{x:Null}" BorderBrush="{x:Null}" 
                        Foreground="{x:Null}" Margin="15" VerticalAlignment="Center" HorizontalAlignment="Center"  
                        MouseLeave="CancelMaterialWindow_Cancel_MouseLeave" 
                        MouseEnter="CancelMaterialWindow_Cancel_MouseEnter" 
                        Click="CancelMaterialWindow_Cancel_Click">
                    <materialDesign:PackIcon Kind="Close" Foreground="Black"/>
                </Button>
            </Grid>
            <Grid Height="60" Margin="0 10 0 0" >
                <Grid.RowDefinitions>
                    <RowDefinition Height="auto"/>
                    <RowDefinition Height="auto"/>
                </Grid.RowDefinitions>
                <StackPanel Orientation="Horizontal" VerticalAlignment="Top" Margin="10 0">
                    <Button x:Name="ContactGrupe_btn" Uid="0" Width="170" Content="КОНТАКТЫ" Height="40" 
                            Background="{x:Null}" BorderBrush="{x:Null}" Foreground="Gray" Click="ContactGrupe_btn_Click"/>
                    <Button Uid="1" Width="170" Content="АДМИНИСТРАТОРЫ" Height="40" Background="{x:Null}" BorderBrush="{x:Null}"
                            Foreground="Gray" Click="ContactGrupe_btn_Click"/>
                </StackPanel>
                <Grid x:Name="GridCursor" Width="170" Height="5" Background="#FF00CC99" HorizontalAlignment="Left"
                      Margin="10 0" Grid.Row="1"/>
            </Grid>
            <Grid x:Name="ChatUsers_Grid" Height="440">
                <Grid.RowDefinitions>
                    <RowDefinition Height="auto"/>
                    <RowDefinition Height="auto"/>
                    <RowDefinition Height="auto"/>
                </Grid.RowDefinitions>
                <Grid Grid.Row="0" Background="White" Height="40" Width="300" Margin="10">
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="auto"/>
                        <ColumnDefinition Width="3*"/>
                        <ColumnDefinition Width="auto"/>
                    </Grid.ColumnDefinitions>
                    <Grid.Effect>
                        <DropShadowEffect BlurRadius="30" ShadowDepth="5" Color="#FFACACAC"/>
                    </Grid.Effect>
                    <TextBlock Text="Петя" Grid.Column="0" HorizontalAlignment="Left" FontSize="25" 
                           VerticalAlignment="Center" Margin="10"/>
                    <Button x:Name="StartChatWithUser_btn" Style="{StaticResource MaterialDesignFloatingActionMiniDarkButton}" Width="30" Height="30"
                            Grid.Column="2" Margin="5" Click="StartChatWithUser_btn_Click">
                        <materialDesign:PackIcon Kind="Telegram" Height="24" Width="24" />
                    </Button>
                </Grid>
            </Grid>
        </StackPanel>

XAML UserControl окна:

<StackPanel x:Name="MessegingWindow" Background="White" >
        <Grid Height="80" Background="White">
            <Grid.Effect>
                <DropShadowEffect BlurRadius="30" ShadowDepth="5" Color="#FFACACAC"/>
            </Grid.Effect>
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="auto"/>
                <ColumnDefinition Width="3*"/>
                <ColumnDefinition Width="auto"/>
            </Grid.ColumnDefinitions>
            <Button x:Name="Return_btn" Grid.Column="0" Style="{StaticResource MaterialDesignFloatingActionMiniAccentButton}" 
                        Width="25" Height="25" Padding="0" Background="{x:Null}" BorderBrush="{x:Null}" 
                        Foreground="{x:Null}" Margin="15" VerticalAlignment="Center" HorizontalAlignment="Center"  
                        Click="Return_btn_Click"
                    >
                <materialDesign:PackIcon Kind="ArrowBack" Foreground="Black" Width="25" Height="25"/>
            </Button>
            <Button Grid.Column="2" Style="{StaticResource MaterialDesignFloatingActionMiniAccentButton}" 
                        Width="25" Height="25" Padding="0" Background="{x:Null}" BorderBrush="{x:Null}" 
                        Foreground="{x:Null}" Margin="15" VerticalAlignment="Center" HorizontalAlignment="Center"  
                        >
                <materialDesign:PackIcon Kind="Close" Foreground="Black"/>
            </Button>
        </Grid>
        <Grid Height="390" Margin="0 10 0 0">
            <TextBlock x:Name="Text"/>
        </Grid>
        <Grid Height="100">
            <Border Margin="5" Background="White" VerticalAlignment="Bottom" Padding="2" CornerRadius="10" >
                <Border.Effect>
                    <DropShadowEffect BlurRadius="30" Color="LightGray" ShadowDepth="0"/>
                </Border.Effect>
                <StackPanel>
                    <Border  Grid.Row="6">
                        <Grid Margin="0 10">
                            <Grid.ColumnDefinitions>
                                <ColumnDefinition Width="*"/>
                                <ColumnDefinition Width="70"/>
                            </Grid.ColumnDefinitions>
                            <TextBox x:Name="Messeg_Txt" MaxHeight="100" TextWrapping="Wrap" Margin="5" 
                                     AcceptsReturn="True" VerticalScrollBarVisibility="Auto" Grid.ColumnSpan="2"
                                     materialDesign:HintAssist.Hint="Введите сообщение*" 
                                     Style="{StaticResource MaterialDesignFloatingHintTextBox}" Foreground="Black"
                                     TextChanged="Messeg_Txt_TextChanged"/>
                        </Grid>
                    </Border>
                </StackPanel>
            </Border>
        </Grid>
        <Grid Height="50">
            <Button x:Name="SendMesseg_Btn" Style="{StaticResource MaterialDesignRaisedButton}" Content="Отправить" Margin="10" Foreground="WhiteSmoke" 
                    Background="#FF33425C" Visibility="Collapsed"/>
            <Button x:Name="SendMessegOff_Btn" Style="{StaticResource MaterialDesignFlatButton}" Content="Отправить" Margin="10" Foreground="DimGray"
                    Background="#FFE0E0E0"/>
        </Grid>
    </StackPanel>