WPF-Set Background color.

<Window x:Class="WpfBackgroundApplication.MainWindow"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         Title="Background" Height="350" Width="525">
    <Grid Background="LightGreen">
        <TextBox HorizontalAlignment="Left" Margin="12,12,0,0" Name="txtDemo" VerticalAlignment="Top" Width="120" Height="25" />
    </Grid>
</Window>