Open byte array Excel

//Read Book (Template)
var excelTemplate=new ExcelReport(_db,_logger) {TemplateId=FdId.FD1210};
byte [ ] buffer = excelTemplate.GetExcelTemplate();
string tempFilePath=System.IO.Path.GetTempFileName();
System.IO.File.WriteAllBytes(tempFilePath, buffer);
XSSFWorkbook book = new XSSFWorkbook (tempFilePath);

// (Something to Do)

// Delete temporary files when finished
System.IO.File.Delete(tempFilePath);