title: Adding items to a menu in a usercontrol
body: <p>I've created a user control with two items: a button and a menu. The code below is a horribly simplified version that still has the same problems (which I will mention below).</p>
  
  <pre><code>&lt;UserControl x:Class="gemsTouchLensApplication.Controls.ButtonAndMenu"
           xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
           xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
           xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
           xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
           mc:Ignorable="d" 
           d:DesignHeight="300" d:DesignWidth="300"&gt;
      &lt;StackPanel Orientation="Horizontal"&gt;
          &lt;Button/&gt;
          &lt;Menu/&gt;
      &lt;/StackPanel&gt;
  &lt;/UserControl&gt;
  </code></pre>
  
  <p>I want to be able to do two things with this usercontrol: add items to the menu and set the content of the button.  </p>
  
  <p>I would like to be able to add items to the menu the conventional way</p>
  
  <pre><code>&lt;Menu&gt;
      &lt;MenuItem Header="1"/&gt;
      &lt;MenuItem Header="2"/&gt;
      &lt;MenuItem Header="3"/&gt;
          &lt;MenuItem Header="4"/&gt;
          &lt;MenuItem Header="5"/&gt;
      etc...
  &lt;/Menu&gt;
  </code></pre>
  
  <p>However, when I try to do this after adding my usercontrol to a stackpanel  </p>
  
  <pre><code>&lt;Window&gt;
      &lt;StackPanel&gt;
          &lt;cntrls:ButtonAndMenu&gt;
              &lt;MenuItem Header="1"/&gt;
              &lt;MenuItem Header="2"/&gt; &lt;!--Comment this out and the error disappears--&gt;
          &lt;/cntrls:ButtonAndMenu&gt;
      &lt;/StackPanel&gt;
  &lt;/Window&gt;
  </code></pre>
  
  <p>something unexpected happens. I can only add a single item to the usercontrol. If I add more than one item I get the error:</p>
  
  <p>Property 'Content' can only be set once.</p>
  
  <p>When only a single item is added the controls visual is closer to that of a button, not a menu.</p>
  
  <p>I suspect that by adding controls to the usercontrol the WPF engine defaults to setting the content of the button instead of adding the controls to the menu.</p>
  
  <p>How can I modify the usercontrol so that the consumer can:  </p>
  
  <ol>
  <li>Add items to the menu using conventional notation </li>
  <li>Still set the content of the button</li>
  </ol>