title: ClosedXML can't delete file after saving Workbook "process in use"
body: <p>So here's the code:</p>
  
  <pre><code>                string filename = @"c:\test.xlsx";
                  using (XLWorkbook wb = CreateWorkbookInformation())
                  {
                      wb.SaveAs(filename);
                      Email.EmailAsAttachment(filename);
                  }
  
                  File.Delete(filename);
  </code></pre>
  
  <p>It creates the Workbook information just fine, it saves the file fine, it emails the file fine as an attachment... However, when I try to delete file (after the <code>using</code> statement), it states the "process is in use".  There shouldn't be anything keeping the file open?!?  What process am I missing that I should close in order to delete the file? </p>