title: Setting a relative column width in XAML. '0.5*' string cannot be converted to Length
body: <p>Here's the XAML:</p>
  
  <pre><code>&lt;ListBox Grid.Row="1" x:Name="lstGames" Background="#343434" &gt;
      &lt;ListBox.ItemTemplate&gt;
          &lt;DataTemplate&gt;
              &lt;Grid ShowGridLines="True"&gt;
                  &lt;Grid.ColumnDefinitions&gt;
                      &lt;ColumnDefinition MaxWidth="0.5*"/&gt; //&lt;-----------HERE!
                      &lt;ColumnDefinition /&gt;
                  &lt;/Grid.ColumnDefinitions&gt;
                  &lt;Grid.RowDefinitions&gt;
                      &lt;RowDefinition /&gt;
                      &lt;RowDefinition /&gt;
                  &lt;/Grid.RowDefinitions&gt;
  
                  &lt;Image Grid.Row="0" Grid.Column="0" Source="{Binding ImageUrl}" Stretch="UniformToFill"/&gt;
                  &lt;StackPanel Grid.Row="0" Grid.Column="1"&gt;
                      &lt;StackPanel Orientation="Horizontal"&gt;
                          &lt;TextBlock Text="Title:" /&gt;
                          &lt;TextBlock Text="{Binding Title}" /&gt;
                      &lt;/StackPanel&gt;
                      &lt;StackPanel Orientation="Horizontal"&gt;
                          &lt;TextBlock Text="Release Date:" /&gt;
                          &lt;TextBlock Text="{Binding ReleaseDate}" /&gt;
                      &lt;/StackPanel&gt;                            
                  &lt;/StackPanel&gt;  
              &lt;/Grid&gt;                    
          &lt;/DataTemplate&gt;
      &lt;/ListBox.ItemTemplate&gt;            
  &lt;/ListBox&gt;
  </code></pre>
  
  <p>All I want is for the first column to at most be around 35% of the total width of the window. I was under the impression that this notation was allowed, but something is wrong and I'm getting that exception fired.</p>
  
  <p>Any suggestions? </p>
  
  <p>If I change it to only <code>Width="0.5*"</code> then it compiles and runs, but still doesn't give the pictures (the columns) a uniform width:</p>
  
  <p><img src="https://i.stack.imgur.com/37Rjc.jpg" alt="enter image description here"></p>