Inserting text box in silver light form threw an exception in visual studio 2012

Question

I am using visual studio 2012.I inserted several lables controls from tool box and it went fine.then I tried to insert tex bocea from the tool bois.

but then when I load the disigner threw an exeptoipon,

Set Property system.windows.Data.Binding.Relativesource thew an exeption.

my XAML is,

<UserControl
    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"
    xmlns:sdk="http://schemas.microsoft.com/winfx/2006/xaml/presentation/sdk" x:Class="acspAdmin.SilverlightControl1"
    mc:Ignorable="d"
    d:DesignHeight="300" d:DesignWidth="400">

    <Grid x:Name="LayoutRoot" Background="White" Margin="0,0,-385,-101">

        <sdk:Label HorizontalAlignment="Left" Height="28" Margin="44,38,0,0" VerticalAlignment="Top" Width="120" Content="E-Mail Address&#xD;&#xA;"/>
        <sdk:Label HorizontalAlignment="Left" Height="28" Margin="44,193,0,0" VerticalAlignment="Top" Width="120" Content="First Name&#xA;"/>
        <sdk:Label HorizontalAlignment="Left" Height="28" Margin="44,103,0,0" VerticalAlignment="Top" Width="120" Content="PassWord&#xA;"/>
        <sdk:Label HorizontalAlignment="Left" Height="28" Margin="44,147,0,0" VerticalAlignment="Top" Width="120" Content="Title"/>
<TextBox />
    </Grid>
</UserControl>