xaml-csharp-development-skill-for-avalonia

WinUI File Pickers, Storage, and Launcher to Avalonia

Table of Contents

1. Scope and APIs
2. Concept Mapping
3. Conversion Example
4. Migration Notes

Scope and APIs

Primary WinUI APIs:

• FileOpenPicker, FileSavePicker, FolderPicker, Launcher, LaunchUriAsync, LaunchFileAsync

Primary Avalonia APIs:

• TopLevel.StorageProvider, IStorageProvider, FilePickerOpenOptions, FilePickerSaveOptions, TopLevel.Launcher, ILauncher

Concept Mapping

WinUI idiom	Avalonia idiom
FileOpenPicker/PickSingleFileAsync	StorageProvider.OpenFilePickerAsync
FileSavePicker/PickSaveFileAsync	StorageProvider.SaveFilePickerAsync
FolderPicker/PickSingleFolderAsync	StorageProvider.OpenFolderPickerAsync
Launcher.LaunchUriAsync	Launcher.LaunchUriAsync
Launcher.LaunchFileAsync(StorageFile)	Launcher.LaunchFileAsync(IStorageItem)

Conversion Example

WinUI XAML:

<StackPanel Spacing="8">
  <Button Content="Open JSON" Click="OpenJson_Click" />
  <Button Content="Open Docs" Click="OpenDocs_Click" />
</StackPanel>

WinUI C#:

var picker = new FileOpenPicker();
picker.FileTypeFilter.Add(".json");
StorageFile? file = await picker.PickSingleFileAsync();
if (file is not null)
    await Launcher.LaunchFileAsync(file);

await Launcher.LaunchUriAsync(new Uri("https://docs.avaloniaui.net"));

Avalonia XAML:

<UserControl xmlns="https://github.com/avaloniaui"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:vm="using:MyApp.ViewModels"
             x:DataType="vm:FilesViewModel">
  <StackPanel Spacing="8">
    <Button Content="Open JSON" Command="{CompiledBinding OpenJsonCommand}" />
    <Button Content="Open Docs" Command="{CompiledBinding OpenDocsCommand}" />
  </StackPanel>
</UserControl>

Avalonia C#:

TopLevel? top = TopLevel.GetTopLevel(this);
if (top is null)
    return;

var files = await top.StorageProvider.OpenFilePickerAsync(new FilePickerOpenOptions
{
    AllowMultiple = false,
    FileTypeFilter = new[]
    {
        new FilePickerFileType("JSON") { Patterns = new[] { "*.json" } }
    }
});

if (files.Count > 0)
    await top.Launcher.LaunchFileAsync(files[0]);

await top.Launcher.LaunchUriAsync(new Uri("https://docs.avaloniaui.net"));

Migration Notes

1. Resolve TopLevel at interaction time and use its StorageProvider/Launcher.
2. Guard picker/launcher flows with capability checks for cross-platform parity.
3. Prefer storage streams and bookmarks over raw path assumptions.

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