title: Can't create Columns in my WPF Grid
body: <p>I have this code for my very <strong>very</strong> basic WPF Project.</p>
  
  <pre><code>&lt;Window x:Class="WpfApplication1.Window1"
  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
  Title="Window1" Height="300" Width="300"&gt;   
  
  &lt;Grid ShowGridLines="True"&gt;
      &lt;ColumnDefinition x:Name="LeftColumn"&gt;&lt;/ColumnDefinition&gt;
  &lt;/Grid&gt;
  </code></pre>
  
  <p></p>
  
  <p>However, the column definition line gives me an error:</p>
  
  <blockquote>
    <p>Error 1   Cannot add instance of type 'ColumnDefinition' to a collection of type 'UIElementCollection'. Only items of type 'UIElement' are allowed.</p>
  </blockquote>