title: Microsoft.Office.Interop.Excel not registered DLL
body: <p>using the <code>Microsoft.Office.Interop.Excel.dll</code> leads to the following error:</p>
  
  <blockquote>
    <p>An unhandled exception of type
    'System.Runtime.InteropServices.COMException' occurred in mscorlib.dll</p>
    
    <p>Additional information: Retrieving the COM class factory for component
    with CLSID {00020819-0000-0000-C000-000000000046} failed due to the
    following error: 80040154 Klasse nicht registriert (Exception from
    HRESULT: 0x80040154 (REGDB_E_CLASSNOTREG)).</p>
  </blockquote>
  
  <p>The error occures in the fourth line of this code:</p>
  
  <pre><code> using EX = Microsoft.Office.Interop.Excel;
  
   private void LoopBANFDokumenteLibrary(System.Uri Link)
   {
          EX.Application MSExcel = new EX.Application();
          EX.Workbook WB = MSExcel.Workbooks.Add(new EX.Workbook()); //ERROR: Exception thrown
          EX.Worksheet WS = WB.Worksheets.Add(new EX.Worksheet());
          /*...and further code...*/
   }
  </code></pre>
  
  <p>Some years ago, I used this Interop.Excel.DLL daily and a never had this problem. Opening regedit.exe, the dll is registered as you can see on this screenshot:</p>
  
  <p><a href="https://i.stack.imgur.com/qL5Q5.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/qL5Q5.png" alt="regedit"></a></p>
  
  <p>Does anybody has an idea, whats wrong?</p>
  
  <p>Regards and thank you,
  Jan</p>