title: Changing build action to "Page" instead of "Content" after web application conversion
body: <p>I have recently converted a website to a web application and after building I see this error:</p>
  
  <p>"Project file must include the .NET Framework assembly 'WindowsBase, PresentationCore, PresentationFramework' in the reference list."</p>
  
  <p>I read around and some have said that there are some aspx files build action that needs to be changed to "Page" instead of "Content". The problem is that there are thousands of files to change. Unsure if the web application conversion was 100% successful.</p>
  
  <p>My idea is to edit the csproj directly, however, I do not know how to do a find and replace for only .aspx files.</p>
  
  <p>e.g.</p>
  
  <pre><code>&lt;Content Include="1/2/3/file.aspx" /&gt;
  &lt;Content Include="h/j/k/file2.aspx" /&gt;
  </code></pre>
  
  <p>to</p>
  
  <pre><code>&lt;Page Include="1/2/3/file.aspx" /&gt;
  &lt;Page Include="h/j/k/file2.aspx" /&gt;
  </code></pre>
  
  <p>I need only to replace aspx files and not .png and .js files etc</p>