Textblock in a viewbox that have no width

Hello my friends,
I wanna wrap the text inside the textblock of my viewbox, but it does not do that :

                    <CheckBox Grid.Row="3" HorizontalContentAlignment="Center" VerticalContentAlignment="Center">
                            <TextBlock Text="Rendre disponible hors-ligne" TextWrapping="Wrap" LineStackingStrategy="BlockLineHeight" LineHeight="15" FontSize="13" FontFamily="Candara Light"/>

If I remove the viewBox, the text do wrap properly.

I saw on the internet that I have to add a width to the viewBox and the textblock, it worked, but I can't do that because the parent will not have the same width depending of the window size.

How can I achieve what I am trying to do ?