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Curiosus.FileDataReaderWriters.Npoi

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NPOI-based IFileWriter implementations that write XLSX files with the streaming workbook (SXSSFWorkbook), keeping only a window of rows in memory. Use it to export large tables to Excel.

Installation​

dotnet add package Curiosus.FileDataReaderWriters.Npoi

Usage​

  • NpoiXlsFileWriter(outputFilePath, logger, rowAccessWindowSize = 100) — one XLSX file, written on Dispose().
  • NpoiXlsMultiFileWriter(savePath, fileName, logger, rowAccessWindowSize = 100) — splits data into report.xlsx, report_part_2.xlsx, ... when a sheet reaches the XLSX row limit (1 048 576) and repeats the headers in every part. Call Flush() to write the last part before disposing.

Numbers, bool, string and DateTime values are written as typed cells (dates use yyyy-MM-dd HH:mm:ss), other values via ToString(); null and whitespace strings leave the cell empty.

using Curiosus.FileDataReaderWriters.Npoi;
using Curiosus.FileDataReaderWriters.Style;
using Curiosus.FileDataReaderWriters.Writers;

using (var writer = new NpoiXlsFileWriter("orders.xlsx", logger))
{
    var bold = writer.AddFormat(new FormatSettings { FontStyle = FontStyle.Bold, FontSize = 12 });
    var money = writer.AddFormat(new FormatSettings { DataFormat = "#,##0.00" });

    writer.AddHeaders(new[] { new CellData("Order", bold), new CellData("Created", bold), new CellData("Total", bold) });
    foreach (var order in orders)
    {
        writer.AppendLine(new[] { new CellData(order.Number), new CellData(order.CreatedAt), new CellData(order.Total, money) });
    }
} // the file is saved here

var multiWriter = new NpoiXlsMultiFileWriter(outputDirectory, "orders.xlsx", logger);
// ... AddHeaders / AppendLine ...
multiWriter.Flush();
multiWriter.Dispose();

See also​