title: WiX close application before uninstall - close open applications message
body: <p>I'm in a kind of misery. I got an installer installing and starting a tray icon app (common .exe)</p>
  
  <p>This is working properly, but now i want to stop that app before this UI telling the user to close the app manually comes up, because during the deinstall routine, my tray icon is removed but the process is still running. </p>
  
  <p>I applied this custom action to close the app before uninstall (or even during)</p>
  
  <pre><code>&lt;CustomAction Id="CloseTrayApp" ExeCommand="-exit" FileKey="TrayApp" Execute="immediate" Return="asyncNoWait" /&gt;
  
  &lt;InstallExecuteSequence&gt;
      &lt;Custom Action="CloseTrayApp" Before="InstallValidate" /&gt;
  &lt;/InstallExecuteSequence&gt;
  </code></pre>
  
  <p>But the "close all running apps" dialog still pops up, but i thought that this will solve my issue. </p>
  
  <p>I already tried to use the CloseAction but i got into a hurry using it because of error while compiling the stuff. It says that the WixUtils namespace may be missing but i double checked that it is there:</p>
  
  <pre><code>xmlns:util="http://schemas.microsoft.com/wix/UtilExtension"
  </code></pre>
  
  <p>How can I avoid the dialog window poping up and trigger this custom action to be executed?</p>