<UserControl x:Class="SilverlightApplication57.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:DesignHeight="300" d:DesignWidth="400">

    <Grid x:Name="LayoutRoot" Background="White">
        <TextBlock Text="{Binding Text}" />
    </Grid>
</UserControl>

namespace SilverlightApplication57 {
    public partial class MainPage : UserControl {
        string _text;
        public string Text { get { return _text; } set { _text = value; } }

        public MainPage() {
            InitializeComponent();
            Text = "Text";
            this.DataContext = this;
        }
    }
}