title: C#: Open Excel (.XLSX) WorkBook => COMException
body: <p>I try to open a .XLSX file from VS2010 .NET 3.5 on a 64bit Windows 7.</p>
  
  <p>Thats the code:</p>
  
  <pre><code>string fileName = string.Format("{0}\\test.xlsx", Directory.GetCurrentDirectory());          
  
              Application _excelApp = new ApplicationClass();
              Workbook workBook = _excelApp.Workbooks.Open(fileName);
  </code></pre>
  
  <p>thats the error I get:</p>
  
  <pre><code>Old format or invalid type library. (Exception from HRESULT: 0x80028018 (TYPE_E_INVDATAREAD))
  </code></pre>
  
  <p>What do I wrong, I go nearly crazy... I tried everything I think at least...</p>