dabble125's answer was perfect, but to give you a sample and mention a note about what matters, where to place the rectangle, see code:
<Grid> <Grid.ColumnDefinitions> <ColumnDefinition/> <ColumnDefinition/> <ColumnDefinition/> </Grid.ColumnDefinitions> <Rectangle Grid.Column="1" Grid.RowSpan="1000"> <Rectangle.Fill> <LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0"> <GradientStop Color="#FF83FF97" Offset="0" /> <GradientStop Color="White" Offset="1" /> </LinearGradientBrush> </Rectangle.Fill> </Rectangle> <TextBlock Grid.Column="1" Text="Some Text"/> </Grid>
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