Add CheckBox to StackPanel
<UserControl x:Class='SilverlightApplication3.MainPage'
xmlns='http://schemas.microsoft.com/winfx/2006/xaml/presentation'
xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'
xmlns:d='http://schemas.microsoft.com/expression/blend/2008'
xmlns:mc='http://schemas.openxmlformats.org/markup-compatibility/2006'
mc:Ignorable='d'
d:DesignWidth='640'
d:DesignHeight='480'>
<StackPanel Background="#ECE9D8">
<TextBlock Margin="3">Look for:</TextBlock>
<ComboBox Margin="3"/>
<TextBlock Margin="3">Filtered by:</TextBlock>
<ComboBox Margin="3"/>
<Button Margin="3,5">Search</Button>
<CheckBox Margin="3">Search in titles only</CheckBox>
<CheckBox Margin="3">Match related words</CheckBox>
<CheckBox Margin="3">Search in previous results</CheckBox>
<CheckBox Margin="3">Highlight search hits (in topics)</CheckBox>
</StackPanel>
</UserControl>
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