Creating automatic resizing of subelements in WPF
I would say no. If you want to create grid-like layout, you should declare columns and rows, and specify how wpf should stretch those. For example like this:

&lt;Grid Margin="30" x:Name="bgBorder"&gt;
    &lt;Grid Background="#555555" x:Name="mainWindow" MouseDown="mainWindow_MouseDown"&gt;
        &lt;Grid.RowDefinitions&gt;
            &lt;!-- frist row will stretch to fit the content --&gt;
            &lt;RowDefinition Height="Auto"/&gt;
            &lt;!-- second row will fill all available space --&gt;
            &lt;RowDefinition Height="*"/&gt;
        &lt;/Grid.RowDefinitions&gt;
        &lt;Grid Margin="2" Grid.Row="0" Height="80" Background="#779999" x:Name="topControl"/&gt;
        &lt;Grid Grid.Row="1"&gt;
            &lt;Grid.ColumnDefinitions&gt;
                &lt;!-- first column will fill all available space --&gt;
                &lt;ColumnDefinition Width="*"/&gt;
                &lt;!-- second column will stretch to fit the content --&gt;
                &lt;ColumnDefinition Width="Auto"/&gt;
            &lt;/Grid.ColumnDefinitions&gt;

            &lt;Grid Grid.Column="0" Margin="2" Background="#557777" x:Name="playListControl"/&gt;
            &lt;Grid Grid.Column="1" Margin="2" Width="234" Background="#668888" x:Name="optionsControl"/&gt;
        &lt;/Grid&gt;
    &lt;/Grid&gt;
&lt;/Grid&gt;


You should really do some reading on how things are done in wpf, this HTML-ish layout you are trying to create won't work.