title: Visual Studio 2012 XAML Designer - Cannot add more than one item
body: <p>I'm new to VS 2012, and I have this issue every time I use the <strong>XAML Designer</strong>.</p>
  
  <p>Every time I add an item (e.g. a RadioButton, and Image, a Label) to my window, it deletes the previous one.</p>
  
  <p>As a result, I can have only one item in my window, I know it is absurd, what am I missing?</p>
  
  <p>Here is the xaml of the window</p>
  
  <pre><code>&lt;Window
      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
      xmlns:WpfViewers="clr-namespace:Microsoft.Samples.Kinect.WpfViewers;assembly=Microsoft.Samples.Kinect.WpfViewers" xmlns:Toolkit="clr-namespace:Microsoft.Kinect.Toolkit;assembly=Microsoft.Kinect.Toolkit" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" mc:Ignorable="d" x:Class="KinectSetupDev.MainWindow"
      Title="MainWindow" Height="400" Width="600"&gt;
      &lt;Toolkit:KinectSensorChooserUI x:Name="SensorChooserUI" VerticalAlignment="Center" Height="40" Margin="277,2,275,328"/&gt;
  &lt;/Window&gt;
  </code></pre>
  
  <p>Here is the xaml of the window after dragging an image on it (from the Toolbox)</p>
  
  <pre><code>&lt;Window
      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
      xmlns:WpfViewers="clr-namespace:Microsoft.Samples.Kinect.WpfViewers;assembly=Microsoft.Samples.Kinect.WpfViewers" xmlns:Toolkit="clr-namespace:Microsoft.Kinect.Toolkit;assembly=Microsoft.Kinect.Toolkit" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" mc:Ignorable="d" x:Class="KinectSetupDev.MainWindow"
      Title="MainWindow" Height="400" Width="600"&gt;
  &lt;Image HorizontalAlignment="Left" Height="86" Margin="77,188,0,0" VerticalAlignment="Top" Width="111"/&gt;
  &lt;/Window&gt;
  </code></pre>