Slcies test

            using var wb = new XLWorkbook();
            var ws = wb.AddWorksheet();

            var data = Enumerable.Range(0, 500000).Select(x => new
            {
                One = 1,
                Two = 2,
                Three = 3,
                Four = 3.14,
                Five = true,
                Six = false,
                Seven = "Hello",
                Eight = Blank.Value
            });
            var ss = Stopwatch.StartNew();
            ws.FirstCell().InsertData(data);
            Console.WriteLine("Insert: Elapsed {0} ms", ss.ElapsedMilliseconds);
            ss.Restart();
            wb.SaveAs(@"c:\Temp\Issues\1969\test.xlsx");
            Console.WriteLine("Save: Elapsed {0} ms", ss.ElapsedMilliseconds);