SpreadSheetTasks

Fast, allocation-conscious .NET support for reading and writing Excel workbooks in .xlsx and .xlsb formats.

SpreadSheetTasks is designed for data pipelines, backend services, command-line tools and applications that need predictable streaming access to Excel data without requiring Microsoft Excel.

Highlights

• Read and write both XLSX and XLSB files.
• Stream rows with typed getters such as GetString, GetInt32, GetDouble and GetDateTime.
• Write from DataTable, IDataReader, object arrays or typed row lists.
• Support multiple sheets, autofilters, hidden sheets and cell formatting.
• Update existing .xlsx and .xlsb sheets while preserving the rest of the workbook.
• Update worksheet-backed pivot-cache ranges and mark dependent pivot tables for refresh.
• Targets net8.0, net9.0 and net10.0.
• NativeAOT and trimming analyzers enabled for the library.

Installation

dotnet add package SpreadSheetTasks --version 1.0.1

Or add the package reference manually:

<PackageReference Include="SpreadSheetTasks" Version="1.0.1" />

Quick start

Write an XLSX or XLSB file

using SpreadSheetTasks;
using System.Data;

var table = new DataTable();
table.Columns.Add("Name", typeof(string));
table.Columns.Add("Age", typeof(int));
table.Rows.Add("Alice", 30);
table.Rows.Add("Bob", 25);

using var writer = new XlsxWriter("people.xlsx"); // or XlsbWriter
writer.AddSheet("People");
writer.WriteSheet(table.CreateDataReader());

Read rows without loading the whole workbook

using SpreadSheetTasks;

using var reader = new XlsxOrXlsbReadOrEdit();
reader.Open("people.xlsx");
reader.ActualSheetName = "People";

while (reader.Read())
{
    string name = reader.GetString(0);
    int age = reader.GetInt32(1);
    Console.WriteLine($"{name}: {age}");
}

Write typed rows

using SpreadSheetTasks;

var headers = new List<string> { "Product", "Price", "Quantity" };
var types = new List<TypeCode> { TypeCode.String, TypeCode.Double, TypeCode.Int32 };
var rows = new List<object?[]>
{
    new object?[] { "Apple", 1.99, 100 },
    new object?[] { "Banana", 0.99, 250 }
};

using var writer = ExcelWriter.CreateWriter("products.xlsx");
writer.AddSheet("Products");
writer.WriteSheet(headers, types, rows, doAutofilter: true);

Update an existing XLSX or XLSB workbook

Use XlsxUpdater for .xlsx and XlsbUpdater for .xlsb. The updater keeps the original package in memory, replaces only the selected worksheet data and related pivot-cache metadata, and does not require Microsoft Excel at runtime:

using SpreadSheetTasks;

var rows = new object?[][]
{
    ["Widget", 50000m],
    ["Gadget", 75000m]
};

using var updater = new XlsxUpdater("report.xlsx"); // XlsbUpdater for .xlsb
updater.ReplaceSheetData("Data", rows,
    new ReplaceSheetDataOptions { Headers = ["Product", "Revenue"] });
updater.Save("report-updated.xlsx");

Save() without an output path safely replaces the source file. ToArray() can be used when the updated package must be handled as bytes. Only .xlsx and .xlsb are supported by the updater API.

NativeAOT and trimming

The package enables the .NET AOT and trimming analyzers and is tested with a published NativeAOT application. The supported package target frameworks are net8.0, net9.0 and net10.0.

For an application, publish for a concrete runtime identifier:

dotnet publish -c Release -r win-x64 --self-contained true -p:PublishAot=true

The repository contains a runnable AOT smoke test covering XLSX, XLSB, DataTable, typed list rows and stream writing. See the complete performance and NativeAOT guide.

Documentation

• Complete usage guide
• Performance and NativeAOT
• GitHub repository
• NuGet package

Performance

The repository includes BenchmarkDotNet projects for regular .NET 10 execution and a focused comparison between .NET 10 JIT and .NET 10 NativeAOT. Benchmark commands, environment details and measured results are maintained in docs/performance-and-aot.md.

Benchmark results depend on CPU, storage, operating system, input files and runtime version. Always reproduce measurements on the target environment before making capacity or latency commitments.

Compatibility notes

Version 1.0.0 introduced the following corrected names:

Previous name	Current name
GetScheetNames()	GetSheetNames()
DocPopertyProgramName	DocPropertyProgramName
SuppressSomeDate	SuppressYear1000Dates
overLimit	maxRows
UseMemoryStreamInXlsb field	UseMemoryStreamInXlsb property

The old members remain available with [Obsolete] warnings where applicable.

License

SpreadSheetTasks is released under the MIT License.