Wpf – HorizontalAlignment=Stretch, MaxWidth, and Left aligned at the same time

alignmentstretchwpfxaml

This seems like it should be easy but I'm stumped. In WPF, I'd like a TextBox that stretches to the width of it's parent, but only to a maximum width. The problem is that I want it to be left justified within its parent. To get it to stretch you have to use HorizontalAlignment="Stretch", but then the result is centered. I've experimented with HorizontalContentAlignment, but it doesn't seem to do anything.

How do I get this blue text box to grow with the size of the window, have a maximum width of 200 pixels, and be left justified?

<Page
  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
  <StackPanel>  
    <TextBox Background="Azure" Text="Hello" HorizontalAlignment="Stretch" MaxWidth="200" />
  </StackPanel>
</Page>

What's the trick?

Best Answer

You can set HorizontalAlignment to Left, set your MaxWidth and then bind Width to the ActualWidth of the parent element:

<Page
  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
  <StackPanel Name="Container">   
    <TextBox Background="Azure" 
    Width="{Binding ElementName=Container,Path=ActualWidth}"
    Text="Hello" HorizontalAlignment="Left" MaxWidth="200" />
  </StackPanel>
</Page>
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