TextBlock with vertical scrollbar only - wpf

Question

I have a TextBlock which may contain a long text so I want to add a vertical scroll bar to it. My initial attempt was to wrap a ScrollViewer around it. That works but the problem is that when I zoom in, the width is zoomed also. I tried disabling the horizontal scroll bar like this:
<ScrollViewer IsTabStop="True" HorizontalScrollBarVisibility="Disabled" VerticalScrollBarVisibility="Auto">
But it didn't solve the problem. I also tried binding the width:
Width="{Binding ElementName=Scroller, Path=ViewportWidth}"
It didn't help either.
So, my question is, how can I add vertical scrollbar to it but have a fixed width and wrapped text for the TextBlock inside? Here's my full code:
<ScrollViewer Grid.Row="1" IsTabStop="True" VerticalScrollBarVisibility="Auto">
<TextBlock HorizontalAlignment="Center" VerticalAlignment="Top" TextWrapping="Wrap" TextAlignment="Center"/>
</ScrollViewer>

Answer 1

There are two parts to this answer... the first is to simply use a TextBox:
<TextBox ScrollViewer.VerticalScrollBarVisibility="Visible" Text="Something really
really really really really really really really really long"
Style="{StaticResource TextBlockStyle}" />
The second part is to simply Style the TextBox so that it looks like a TextBlock:
<Style x:Key="TextBlockStyle" TargetType="{x:Type TextBox}">
<Setter Property="Background" Value="{x:Null}" />
<Setter Property="BorderBrush" Value="{x:Null}" />
<Setter Property="BorderThickness" Value="0" />
<Setter Property="Padding" Value="0" />
<Setter Property="IsReadOnly" Value="True" />
<Setter Property="IsTabStop" Value="False" />
<Setter Property="VerticalAlignment" Value="Center" />
<Setter Property="SnapsToDevicePixels" Value="True" />
<Setter Property="TextWrapping" Value="Wrap" />
<Style.Triggers>
<Trigger Property="IsEnabled" Value="False">
<Setter Property="Background" Value="{x:Null}" />
</Trigger>
</Style.Triggers>
</Style>
Feel free to remove any of these properties if they do not suit your situation.

Answer 2

<TextBox HorizontalAlignment="Center"
VerticalAlignment="Top"
TextWrapping="Wrap"
TextAlignment="Center"
VerticalScrollBarVisibility="Auto" Width="300" Style="{StaticResource TextBlockStyle}"/>
You don't need a ScrollViewer wrapped in the TextBox, the TextBox control has its own ScrollViewer. And you need to define the width of the TextBox so that the scrollbar will know its fixed width and will wrap the text.
Then, you have to style the TextBox to look like a TextBlock
A good reason why this ScrollViewer won't work according to to Ifeanyi Echeruo from Microsoft, from MSDN
ScrollViewer first asks its content how large it would like to be in
the absence of constraints, if the content requires more space than
the Viewer has then its time to kick in some ScrollBars
In the absence of constraints TextBlock will always opt to return a
size where all text fits on a single line.
A ScrollViewer with ScrollBars will never get a TextBlock to wrap.
However you may be able to come up with a Measure\Arrange combination
for a panel of your own that is almost like ScrollViewer but I cant
think of any logic that can satify both constraints without explicit
knowlege of the behaviour of said children