Text wrapping in textbox contained in Rafting Window

I have a ToolWindow. It countains a UserControl which then contains a Textbox. I want the text to wrap in the textbox but I do not want to set the width of the textbox. The textbox should stretch and shrink when user resize the toolwindow.

I was able to havethis functionality easily using a WPF window:

<Window x:Class="WpfApplication2.MainWindow"

xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

ResizeMode="CanResizeWithGrip"

Title="MainWindow" Height="350" Width="525">

<Grid>

<TextBox Name="textBox1" VerticalAlignment="Top" TextWrapping="Wrap" HorizontalAlignment="Stretch" />

</Grid>

</

Window>

But I cannot get the same functionality with a tool window. I tried:

window.Float((

Size) arg);

var baseWindow = Window.GetWindow(window);

if (baseWindow != null)

{

baseWindow.ResizeMode = ResizeMode.CanResizeWithGrip;

}

But that did not help at all.

Is there a way?