title: Excel Add-In - ClickOnce - VSTOInstaller.exe.config file, what is it?
body: <p><strong>EDIT :</strong> Looks like a Microsoft issue, see forum indicated by correct answer. </p>
  
  <p><strong>EDIT 2:</strong> I am going to stop monitoring this page, looks like the Microsoft forum is dead and I also don't work for the same company anymore.</p>
  
  <hr>
  
  <p>We have a Excel Add-in (C# / .NET 4.0) which supports Excel 2007/2010/2013 and is deployed through Excel Add-In. Today, a new client ran into problems on a single machine (other machines installed the add-in correctly). The error was:</p>
  
  <blockquote>
    <p>The value of the property 'type' cannot be parsed. The error is: Could
    not load file or assembly 'Microsoft.Office.BusinessApplications.Fba,
    Version=14.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c' or
    one of its dependancies. The system cannot find the file specified.
    (C:\Program Files (x86)\Common Files\Microsoft
    Shared\VSTO\10.0\VSTOInstaller.exe.Config line 10)</p>
  </blockquote>
  
  <p>My buddy Google gave me a number of suggestions: We had the client try a repair of MS VSTO Tools for Office and a repair of Office, and had the IE cache cleared, but continued to get the same error. Finally, we tried re-naming the VSTOInstaller.<strong>exe</strong>.Config to 'hide' it from the installation and it appears to be working.</p>
  
  <p>I don't believe that our Add-In or installation produces this file, and there is no dependancies on this file that I'm aware of (it appears to be related to a SharePoint assembly)</p>
  
  <p>While I don't explicitly download the add-in myself (I run it through VS2013), I have a VSTOInstaller.config file (Note, not *.exe.config, as seen from client) which contains the following XML:</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8" ?&gt;
  &lt;configuration&gt;
    &lt;system.net&gt;
      &lt;webRequestModules&gt;
        &lt;remove prefix="http:"/&gt;
        &lt;remove prefix="https:"/&gt;
        &lt;add prefix="http:"
             type="Microsoft.Office.BusinessApplications.Runtime.DeploymentAction.HttpFbaRequestCreator,Microsoft.Office.BusinessApplications.Runtime,Version=14.0.0.0,Culture=neutral,PublicKeyToken=71e9bce111e9429c" /&gt;
        &lt;add prefix="https:"
             type="Microsoft.Office.BusinessApplications.Runtime.DeploymentAction.HttpFbaRequestCreator,Microsoft.Office.BusinessApplications.Runtime,Version=14.0.0.0,Culture=neutral,PublicKeyToken=71e9bce111e9429c" /&gt;
      &lt;/webRequestModules&gt;
    &lt;/system.net&gt;
  &lt;/configuration&gt;
  </code></pre>
  
  <p>In order to get a better idea of why this client is getting the specified error, I'm looking into</p>
  
  <ol>
  <li>Where this file could have come from. </li>
  <li>How does it affect the installation.</li>
  <li>Any other comments or general tips related to the exception, or better yet, how to avoid it altogether.</li>
  </ol>