title: EPPlus: Saving after setting ExcelDxfStyleConditionalFormatting
body: <p>I created a method for reformatting an Excel Workbook:</p>
  
  <pre><code>        string Formula = @"IF(LEN($A2)&gt;0,1,0)";
  
          using (ExcelPackage excelFile = new ExcelPackage(destinationfile))
          {
              ExcelWorksheet worksheet = excelFile.Workbook.Worksheets[1];
              ExcelTable worktable = worksheet.Tables[0];
              string workrange = worksheet.Cells[worktable.Address.Start.Row + 1, worktable.Address.Start.Column, worktable.Address.End.Row, worktable.Address.End.Column].Address;
  
              ExcelAddress cellIsAddress = new ExcelAddress(workrange);
              var cfRule = worksheet.ConditionalFormatting.AddExpression(cellIsAddress);
  
              cfRule.Formula = Formula;
  
              //cfRule.Style.Fill.PatternType = ExcelFillStyle.Solid;
              //cfRule.Style.Fill.PatternColor.Color = Color.LightYellow;
              //cfRule.Style.Fill.BackgroundColor.Auto = true;
              //cfRule.Style.Font.Bold = true;
              //cfRule.Style.Fill.BackgroundColor.Color = Color.LightCyan;
  
              excelFile.Save();
          }
  </code></pre>
  
  <p>The problem is that, if I set any style to the rule (My goal was to set a yellow background, but I also tried with all the commented options), the Save() method crashes.
  Any ideas?</p>