title: Web.Debug.config not processing substitution
body: <p>I have a web application in VS2010 with a web.config like this:</p>
  
  <pre><code>...
  &lt;configuration&gt;
    &lt;connectionStrings&gt;
      &lt;add name="ApplicationServices"
           connectionString="data source=MyProdDb;Initial Catalog=MyCat;User Id=MyUser;Password=MyPass;"
           providerName="System.Data.SqlClient" /&gt; 
    &lt;/connectionStrings&gt;
  ...
  </code></pre>
  
  <p>and a Web.Debug.config like this:</p>
  
  <pre><code>...
  &lt;configuration xmlns:xdt="http://schemas.microsoft.com/XML-Document-Transform"&gt;
      &lt;connectionStrings&gt;
          &lt;add name="ApplicationServices"
            connectionString="data source=MyDevDb;Integrated Security=SSPI;AttachDBFilename=|DataDirectory|aspnetdb.mdf;User Instance=true"
            xdt:Transform="SetAttributes" xdt:Locator="Match(name)"/&gt;
      &lt;/connectionStrings&gt;
  ...
  </code></pre>
  
  <p>The project is set to create a Debug build, and when I run it in the debugger, I get <code>MyProdDb</code> rather than <code>MyDevDb</code></p>
  
  <p>What am I missing?</p>