Devolutions.AvaloniaControls.SpreadsheetEditor 2026.9.28

Devolutions.AvaloniaControls.SpreadsheetEditor

An Excel-like spreadsheet editor control for Avalonia UI. It uses a custom grid (not the Avalonia DataGrid) so cells can merge and host rich content, and it ships with:

• A custom rendering grid with cell merging, frozen headers, and drag-to-select.
• Rich in-cell editing (bold/italic/underline/strikethrough, fonts, colors, alignment).
• A hand-rolled = formula engine (arithmetic, ranges, SUM/AVERAGE/IF/…, named ranges, live recalc).
• Charts, multi-sheet tabs, infinite rows/columns, undo/redo, clipboard, and printing (cross-platform PDF export + HTML preview).

Requirements

This control depends on the commercial Avalonia Accelerate packages (Avalonia.Controls.RichTextEditor, Avalonia.Controls.Charts). You must supply your own Avalonia UI license key (via the <AvaloniaUILicenseKey> MSBuild item or the standard licensing mechanism) in the application that consumes this control. See https://avaloniaui.net/.

Setup

Add the required theme includes to your App.axaml (alongside FluentTheme):

<Application.Styles>
    <FluentTheme />
    <StyleInclude Source="avares://Avalonia.Controls.RichTextEditor/Themes/Default.axaml" />
    <StyleInclude Source="avares://Avalonia.Controls.Charts/Themes/Default.axaml" />
</Application.Styles>

Usage

xmlns:se="clr-namespace:SpreadsheetEditor.Controls;assembly=SpreadsheetEditor.Controls"
...
<se:SpreadsheetEditor x:Name="Editor" />

The control exposes an integration API similar to Avalonia's RichTextEditor: IsReadOnly, Undo()/Redo() + CanUndo/CanRedo, SelectAll(), SelectedRange, and the ContentChanged, SelectionChanged, and IsReadOnlyChanged events. Load data via LoadSheet, LoadWorkbook, LoadCellData, or LoadRows; read it back with GetCellData/GetRows.

Excel (.xlsx) files — included

Excel read/write is built in (backed by ClosedXML plus OOXML chart parsing), so no extra package is needed:

using System.IO;

// Load an .xlsx (every worksheet → one tab) into the control:
await using (FileStream fs = File.OpenRead("book.xlsx"))
    await editor.OpenXlsxAsync(fs); // keeps the UI responsive for large workbooks

// Save the active sheet back to .xlsx:
await using (FileStream fs = File.Create("out.xlsx"))
    editor.SaveXlsx(fs);

OpenXlsx(Stream) remains available for synchronous callers.

OpenXlsxAsync reads workbook tab names and colors immediately, then reads roughly one visible viewport of the first worksheet, including its cached Excel formula results and charts. Other worksheets remain lightweight, correctly styled placeholders until selected. Selecting a tab displays its viewport-sized preview first and starts only that worksheet's full-fidelity import in the background. The previous frame stays visible until that preview is ready, avoiding a placeholder flash during the handoff. Preview sheets are read-only until their complete data is ready. A single serialized ClosedXML reader is reused for the workbook, so browsing several tabs does not queue repeated full-workbook parses. Opening a workbook preserves Excel's saved formula results instead of recalculating every sheet. After a cell edit, any worksheet needed by a sheet-qualified reference such as Users!A1 loads on demand, then the affected formulas recalculate.

For headless / non-UI use, the readers/writers are also available directly via SpreadsheetEditor.Controls.Xlsx.XlsxFile (ReadWorkbook/Read/Write) returning the library's SheetData model.

Printing (cross-platform)

Avalonia has no built-in print API, so the control offers two portable routes — both work on Windows, macOS, and Linux:

using System.IO;

// 1. PDF export (recommended). Self-contained, rendered with SkiaSharp — no browser needed.
//    Cell fills, borders, alignment, and rich run formatting are preserved; the sheet is scaled
//    to fit the page width and rows flow across pages.
await using (FileStream fs = File.Create("sheet.pdf"))
    editor.ExportPdf(fs);

editor.SavePdf("sheet.pdf");   // convenience overload for a file path
editor.PrintPdf();             // writes a temp PDF and sends it to the printer (see below)

// 2. HTML preview. Opens the sheet in the default browser, where the user prints (or saves a PDF)
//    via the browser's own print dialog.
string html = editor.ExportHtml();
editor.Print();

PrintPdf() sends the PDF straight to the printer: on Windows via the shell "print" verb (the registered PDF handler prints to the default printer), and on Linux/macOS via lpr (the default CUPS printer). Print() instead opens the HTML in the default browser (ShellExecute/open/xdg-open) for browser-driven printing. Images are not drawn into the PDF/HTML (data only); charts are included in the PDF.