Gembox.spreadsheet.dll 💯

var worksheet = reader.Worksheets[0]; foreach (var row in worksheet.Rows) // Process row by row without holding entire file in RAM Console.WriteLine(row.Cells[0].Value);

using (var reader = ExcelFile.LoadXlsx("hugefile.xlsx", new XlsxLoadOptions ReadDataOnly = true )) gembox.spreadsheet.dll

HorizontalAlignment = HorizontalAlignmentStyle.Center, FillPattern = FillPatternStyle.Solid, FillPatternForegroundColor = SpreadsheetColor.FromName(ColorName.DarkBlue), FontColor = SpreadsheetColor.FromName(ColorName.White) ; worksheet.Cells.GetSubrange("A1:D1").Style = headerStyle; var worksheet = reader

A unique feature of this DLL is direct HTML rendering: var worksheet = reader.Worksheets[0]

workbook.Save("Report.xlsx"); For truly massive files (500k+ rows), use the LoadOptions to stream data:

var workbook = new ExcelFile(); var worksheet = workbook.Worksheets.Add("Sales Report");