title: Update ContentPages when MasterPage changed
body: <p>Started a new project and first created a MasterPage. Immediately I then created a ContentPage using MasterPage. I then realised I forgot to add ContentPlaceHolder controls in the MasterPage, so I added them. Rebuilding the project did not add these controls to the content page.</p>
  
  <p>As it is a new project, I can easily delete the ContentPage and readd it, but for convenience in the future, especially for larger projects, is there any way to automate this process without having to recreate the ContentPage/manually type the ContentPlaceHolder controls within the ContentPages?</p>
  
  <p>Thanks.</p>