title: VS2017 Installer project output does not replace the current installation
body: <p>I have a standard windows forms application that is being deployed using the VS2017 setup project. When opening the setup project using the "File System", I added to the application folder the following:</p>
  
  <ol>
  <li>Primary output from the win forms app.</li>
  <li>The <code>EPPlus</code> library's dll.</li>
  <li>Some excel files.</li>
  </ol>
  
  <p>The setup project gives the output <code>.msi</code> package just fine. The problem is, when I run the <code>.msi</code> output after building the setup project (of course after building the source project) and run the application, I do not see my updates, even the files on <code>C:\Program Files ....</code> directory are not modified. I tried changing the product code and the increasing the version and it does not work. My questions are:</p>
  
  <ol>
  <li>Besides removing and installing the program again, is there anyway to make the installer package actually updating the software's installation?</li>
  <li>How to avoid the problem in #1 no matter how much I update the software?</li>
  <li>What is the cause and how to avoid this error "Another version of this product is already installed"? I'm not sure of what I did for it to pop up.</li>
  <li>If I want some part of the source code to be in a separate dll, is it as simple as adding a class library project and adding its output to the setup project?</li>
  </ol>
  
  <p>Thank you very much.</p>