title: AlternateContent question
body: <p>In xaml code I want to use certain buttons for instance or not based upon the whether there is a certain preprocessor attribute defined. So I'm trying to do a preprocessor thing in the xaml.Sorry this might not be compilable but it's a pretty simple example.</p>
  
  <p>What I want to do is in the AssemblyInfo.cs for the project that the .xaml code resides</p>
  
  <pre><code>#if A_PROJECT
  [assembly: XmlnsDefinitionAttribute("A_PROJECT", "A.PROJECT.NAMESPACE")]
  #endif
  
  #if B_PROJECT
  [assembly: XmlnsDefinitionAttribute("B_PROJECT", "B.PROJECT.NAMESPACE")]
  #endif
  </code></pre>
  
  <p>IN THE XAML</p>
  
  <p>
  
  <p>I want to use AButton if A Project other wise I don't want to use this button in view</p>
  
  <pre><code>   &lt;Button x:Name="AButton"/&gt;
  </code></pre>
  
  <p>I tried using the following but I get compile error trying to reference buttton</p>
  
  <pre><code>   &lt;mc:AlternateContent&gt;
        &lt;mc:Choice Requires="a_project"&gt;
           &lt;Button x:Name="AButton"/&gt;
        &lt;/mc:Choice&gt;
     &lt;/mc:AlternateContent&gt;
  </code></pre>
  
  <p>IN THE XAML.CS </p>
  
  <p>There is a compile error trying to reference button</p>