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POGrid inside a StackPanel: why do auto and * behave strangely?
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  1. POGrid inside a StackPanel: why do auto and * behave strangely?
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    copied!<p>My google and stackoverflow search-fu have failed me, so I present to the community this question.</p> <p>(This is all generated using VS2010 and .NET 4.0, in a blank default WPF Solution)</p> <p>Consider the following XAML:</p> <pre><code>&lt;StackPanel Orientation="Horizontal"&gt; &lt;Grid&gt; &lt;Grid.ColumnDefinitions&gt; &lt;ColumnDefinition Width="20"/&gt; &lt;ColumnDefinition Width="*"/&gt; &lt;/Grid.ColumnDefinitions&gt; &lt;Border Name="aborder" Grid.Column="0" Grid.ColumnSpan="2" Background="Red" Width="200"/&gt; &lt;Border Name="aborder2" Background="Green"/&gt; &lt;/Grid&gt; &lt;/StackPanel&gt; </code></pre> <p>What would you predict the width of "aborder2" to be? </p> <p>If you guessed "20 pixels", you would be wrong. The correct answer is 110 pixels.</p> <p>Consider this XAML:</p> <pre><code> &lt;StackPanel Orientation="Horizontal"&gt; &lt;Grid&gt; &lt;Grid.ColumnDefinitions&gt; &lt;ColumnDefinition Width="20"/&gt; &lt;ColumnDefinition Width="Auto"/&gt; &lt;/Grid.ColumnDefinitions&gt; &lt;Border Name="aborder" Grid.Column="0" Grid.ColumnSpan="2" Background="Red" Width="200"/&gt; &lt;Border Name="aborder2" Background="Green"/&gt; &lt;/Grid&gt; &lt;/StackPanel&gt; </code></pre> <p>What would you predict the width of "aborder2" to be?</p> <p>If you guessed either 20 pixels or 110 pixels, you would be wrong. The correct answer is 200 pixels.</p> <p>I cannot figure this out and it's driving me insane. It seems like the answer should be obvious; clearly there's some interaction between an auto-filling grid column and the stackpanel that causes the grid to freak out. But it just doesn't seem to make <em>sense</em> - whatever rules are governing this behavior seem to be arbitrary. Why 110 pixels? Why not 109 pixels or 100 pixels? I would understand if the auto-sized column failed to expand fully or something, but to have the fixed-width column randomly ignore its width has left me a burnt out shell of a developer.</p> <p>Any help or guiding lights would be much appreciated!</p>
 

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