AvaloniaMessageBox

A flexible and modern modal message box implementation for Avalonia UI 11.2+.

Supports:

• Classic Desktop applications (IClassicDesktopStyleApplicationLifetime)
• Single view apps (ISingleViewApplicationLifetime)
• Early fallback before MainWindow or MainView is ready
• Native Fallback to OS API com P/Invoke para macOS, Windows e X11/Linux if avalonia is not avaliable
• DPI-aware sizing and theme-aware font and styling
• Optional icons and multi-line messages
• Modal behavior even in SingleView via panel overlay

✨ Features

• Compatible with .NET 9 and Avalonia 11.2+
• Fully theme-aware (fonts, colors, shadows)
• Automatically localizes button text (Yes, No, OK, Cancel) using CultureInfo.CurrentUICulture
• Supports:
  • OK
  • OK / Cancel
  • Yes / No
• Built-in modern emoji-based icons:
  • ℹ️ Info
  • ⚠️ Warning
  • ❌ Error
  • ✅ Success
  • ❓ Question
  • 🛑✋ Stop (hand over stop sign with overlay)
• Works even before MainWindow or MainView is set

🌍 Localization Support

Button labels (OK, Cancel, Yes, No) are automatically translated based on the current UI culture (CultureInfo.Current).
Includes built-in translations for over 68 languages, including:

• pt-BR → "Sim", "Não", "OK", "Cancelar"
• es → "Sí", "No", "OK", "Cancelar"
• fr → "Oui", "Non", "OK", "Annuler"
• de → "Ja", "Nein", "OK", "Abbrechen"
• ja → "はい", "いいえ", "OK", "キャンセル"
• ...and many others

No configuration needed — just set the culture in your app startup code:

🚀 Use

await MessageBox.ShowAsync(
    parent: this, // Pode ser Window ou UserControl
    title: "Atenção",
    message: "Tem certeza que deseja continuar?",
    buttons: MessageBoxButtons.YesNo,
    icon: MessageBoxIcon.Question);

You can call it even before setting MainWindow in your App.cs:

Automatic Fallback to native os MessageBox if Avalonia is not ready

await MessageBox.ShowAsync(null, "Erro de Inicialização", "Configuração inválida.");

🛑 ExceptionMessageBox - Show Exception with details

try
{
    // ...
}
catch (Exception ex)
{
    await ExceptionMessageBox.ShowExceptionDialogAsync(this, ex);
}

Includes name of exception, line of error, filename and exception message.

📦 Install

✅ NuGet

dotnet add package CastelloBranco.AvaloniaMessageBox

Or in .csproj:

<PackageReference Include="CastelloBranco.AvaloniaMessageBox" Version="1.0.0" />

📄 License

MIT License
(c) 2025 Castello Branco Tecnologia

🏷️ Crédits

Created and mainteined by Castello Branco Tecnologia

GitHub - CastelloBrancoTecnologia/AvaloniaMessageBox