title: WiX: How do I show the EULA agreement UI during an upgrade?
body: <p>I use WiX to create and build my Windows app MSI installer. My <strong>Product.wxs</strong> file has the following structures to customise the installer, including the display of a custom EULA:</p>
  
  <pre><code>&lt;WixVariable Id="WixUIBannerBmp" Value="MyBanner.bmp" /&gt;
  &lt;WixVariable Id="WixUIDialogBmp" Value="MyDialog.bmp" /&gt;
  &lt;WixVariable Id="WixUIInfoIco" Value="MyIcon.ico" /&gt;
  &lt;WixVariable Id="WixUILicenseRtf" Value="MyEULA.rtf" /&gt;
  </code></pre>
  
  <p>It uses the 'InstallDir' built-in WiX UI dialog set:</p>
  
  <pre><code>&lt;UI&gt;
    &lt;UIRef Id="WixUI_InstallDir" /&gt;
  &lt;/UI&gt;
  </code></pre>
  
  <p>This all works fine for fresh installations.</p>
  
  <p>When I release an <em>upgrade</em> to my application, to date, I have been using the following command to execute without a UI it as part of the upgrade process:</p>
  
  <pre><code>msiexec /i MyInstaller.msi REINSTALL=ALL REINSTALLMODE=vemus /passive
  </code></pre>
  
  <p><strong>I now want to change my EULA, and on the next [minor] upgrade, have the user be asked to agree to the EULA again. How do I do this?</strong></p>
  
  <p>(I removed the <code>/passive</code> switch from the command above and the updater MSI now has a UI, but it does not show the EULA agreement UI – it only does so on a fresh install.)</p>