xaml-csharp-development-skill-for-avalonia

WPF Interop (HwndHost/Win32) and Native Hosting to Avalonia

Table of Contents

1. Scope and APIs
2. Interop Mapping
3. Conversion Example
4. Avalonia C# Equivalent
5. Troubleshooting

Scope and APIs

Primary WPF APIs:

• HwndHost
• WindowInteropHelper
• WindowsFormsHost

Primary Avalonia APIs:

• NativeControlHost
• platform handles (IPlatformHandle)
• TopLevel and platform features

Interop Mapping

WPF	Avalonia
HwndHost for native child window	NativeControlHost
direct window handle interop helper	TopLevel/platform-handle access paths
WindowsFormsHost	explicit native-host integration layer

Conversion Example

WPF C#:

public sealed class NativePreviewHost : HwndHost
{
    protected override HandleRef BuildWindowCore(HandleRef hwndParent)
    {
        // create child HWND
    }
}

Avalonia XAML:

<local:NativePreviewHost xmlns="https://github.com/avaloniaui"
                         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                         xmlns:local="using:MyApp.Controls" />

Avalonia C# Equivalent

using Avalonia.Controls;
using Avalonia.Controls.Platform;
using Avalonia.Platform;

public sealed class NativePreviewHost : NativeControlHost
{
    protected override IPlatformHandle CreateNativeControlCore(IPlatformHandle parent)
    {
        // create platform-native child and return its handle wrapper.
        return base.CreateNativeControlCore(parent);
    }

    protected override void DestroyNativeControlCore(IPlatformHandle control)
    {
        // release native resources allocated in CreateNativeControlCore.
        base.DestroyNativeControlCore(control);
    }
}

Troubleshooting

1. hosted native view stays hidden.
   • ensure host has non-zero size and is attached to a live TopLevel.
2. crashes on close/reparent.
   • centralize ownership and teardown in DestroyNativeControlCore.
3. behavior differs by platform.
   • isolate interop behind adapters and keep the app-facing interface stable.

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