OpenStandardLibrary 1.0.2

Open Standard Library

A .NET library for reading and creating spreadsheet files in ODS, XLSX, and delimited formats (CSV, TSV, pipe-delimited). No external dependencies — just pure .NET.

Supported Formats

Features

• Multi-sheet workbooks — create and import workbooks with multiple named sheets
• Cell value types — String, Float, Boolean, DateTime, and Int64
• Cell styling — bold, italic, underline, font color/name/size, background color, borders (thin/medium/thick with color per edge), and text wrapping
• Column widths — manual SetColumnWidth() or automatic AutoFitColumns() with min/max constraints
• Freeze panes — freeze rows and/or columns with FreezeRows and FreezeColumns
• Auto-filters — SetAutoFilter() for the full range or a custom range
• Header row detection — HasHeaderRow, HeaderNames, and GetColumn(string) for column-name-based access. Auto-detected on XLSX/ODS import when freeze panes or auto-filters are present
• Streaming CSV reader — ReadCsvRowsAsync() reads rows one at a time via IAsyncEnumerable with optional header detection and row limit
• File encoding options — UTF-8 (default), ASCII, Unicode (UTF-16), and UTF-32 for delimited files
• Epoch conversion — FromEpochSeconds(), FromEpochMilliseconds(), ToEpochSeconds(), ToEpochMilliseconds() extension methods on cells
• Formulas — set formula expressions on cells
• Dependency injection — implements ISpreadsheet with IDisposable/IAsyncDisposable

Installation

dotnet add package OpenStandardLibrary

Quick Start

Generate an XLSX file

using OoxSpreadsheet;
using OslSpreadsheet.Models;

using var spreadsheet = new Spreadsheet();
var sheet = spreadsheet.Workbook.AddSheet("Data");

sheet.AddCell(1, 1, "Name");
sheet.AddCell(1, 2, "Score");
sheet.AddCell(2, 1, "Alice");
sheet.AddCell(2, 2, "95.5", CellValueType.Float);

var bytes = await spreadsheet.GenerateXlsxFileAsync();
await File.WriteAllBytesAsync("output.xlsx", bytes);

Import and read by column name

using var spreadsheet = new Spreadsheet();
var workbook = await spreadsheet.ImportXlsxFileAsync(File.ReadAllBytes("input.xlsx"));
var sheet = workbook.Sheets[0];

// HasHeaderRow is auto-detected from freeze panes or auto-filters
if (sheet.HasHeaderRow)
{
    var names = sheet.GetColumn("Name");
    foreach (var cell in names)
        Console.WriteLine(cell.Value);
}

Stream CSV rows

using var spreadsheet = new Spreadsheet();
using var stream = File.OpenRead("large-file.csv");

await foreach (var row in spreadsheet.ReadCsvRowsAsync(stream, hasHeaderRow: true, rowLimit: 100))
{
    Console.WriteLine(string.Join(", ", row));
}

// Headers are available after iteration
Console.WriteLine($"Columns: {string.Join(", ", spreadsheet.CsvHeaders!)}");

Cell styling

var cell = sheet.AddCell(1, 1, "Header");
cell.Style = new CellStyle
{
    Bold = true,
    FontColor = "#FFFFFF",
    BackgroundColor = "#2196F3",
    BorderBottom = new CellBorder { Style = BorderStyle.Medium, Color = "#1565C0" },
    WrapText = true
};

Epoch conversion

var cell = sheet.AddCell(1, 1, "1747650600");
cell.FromEpochSeconds(); // Value becomes "2025-05-19T10:30:00", ValueType becomes DateTime

// Or convert back
cell.ToEpochSeconds(); // Value becomes "1747650600", ValueType becomes Int64

Supported Frameworks

• .NET 8.0
• .NET 9.0
• .NET 10.0

Disclaimer

This software is provided "as is", without warranty of any kind. Use at your own risk. See the LICENSE file for full terms.

License

MIT