Textbox does not show a verticalscrollbar - wpf

Question

<Window
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d" x:Class="WpfApplication1.MainWindow"
Title="MainWindow" Height="350" Width="550" MinHeight="350">
<DockPanel Background="BlanchedAlmond">
<DataGrid Background="YellowGreen" DockPanel.Dock="Top" MinHeight="100">
</DataGrid>
<StackPanel DockPanel.Dock="Bottom" Orientation="Horizontal" FlowDirection="RightToLeft" Margin="10" Background="YellowGreen">
<Button HorizontalAlignment="Right" Click="Button1Add_Click" Margin="5,0">Add text 1</Button>
<Button HorizontalAlignment="Right" Click="Button2Add_Click">Add text 2</Button>
<Button HorizontalAlignment="Right" Click="Button1_Click" Margin="5,0">Toggle textbox 1</Button>
<Button HorizontalAlignment="Right" Click="Button2_Click">Toggle textbox 2</Button>
</StackPanel>
<Grid Background="Red">
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
</Grid.RowDefinitions>
<TextBox x:Name="TextBox1" Grid.Row="0" Background="AliceBlue" HorizontalScrollBarVisibility="Auto" VerticalScrollBarVisibility="Auto">Test 1</TextBox>
<TextBox x:Name="TextBox2" Grid.Row="1" Background="AliceBlue" HorizontalScrollBarVisibility="Auto" VerticalScrollBarVisibility="Auto">Test 2</TextBox>
</Grid>
</DockPanel>
</Window>
In the example above I am trying to achieve that the two textboxes in the middle just fill the available space between the top datagrid and the bottom stackpanel with buttons.
They have to divide that space between them depending on their text-content and their visibility.
Both properties can change by databindings, I simulated that with the click events.
But when the space is filled up they have to show a vertical scrollbar when needed.
The code sample above is not good. When I add text to a textbox, the grid-row becomes larger but disappears from the visible region, no scroll bar.
EDIT: I ended up with:
<ScrollViewer Background="AliceBlue" VerticalScrollBarVisibility="Auto">
<StackPanel Orientation="Vertical">
<Label x:Name="Label1" Margin="0,6,0,0">Test 1:</Label>
<TextBox x:Name="TextBox1" Padding="0,6"></TextBox>
<Label x:Name="Label2" Margin="0,6,0,0">Test 2:</Label>
<TextBox x:Name="TextBox2" Padding="0,6" ></TextBox>
</StackPanel>
</ScrollViewer>

Answer 1

You need to add a ScrollViewer in your XAML around the content.
ScrollViewer on MSDN
<ScrollViewer>
Content
</ScrollViewer>