Breaking Changes in v5.0.0

This page lists all breaking changes between AvalonDock v4.x and v5.0.0, organized by category.

Package Structure

Serializers Extracted to Separate Packages

Impact: High — affects all projects using layout serialization.

The XML layout serializer has been moved from the core AvalonDock package to AvalonDock.Serializer.Xml. A new JSON serializer is available in AvalonDock.Serializer.Json.

Change	Details
Removed from	`Dirkster.AvalonDock`
Moved to	`Dirkster.AvalonDock.Serializer.Xml`
Old namespace	`AvalonDock.Layout.Serialization`
New namespace	`AvalonDock.Serializer.Xml`
Fix	Install the serializer package and update `using` statements.

- using AvalonDock.Layout.Serialization;
+ using AvalonDock.Serializer.Xml;

New Core Package

Impact: Low — automatically referenced.

A new AvalonDock.Core package contains UI-agnostic interfaces and models. It is automatically referenced by AvalonDock, so no explicit installation is needed.

Architecture

ILayoutEngine Introduction

Impact: Low to Medium — only affects custom layout logic.

The layout calculation logic has been formalized behind the ILayoutEngine interface.

Change	Details
Added	`ILayoutEngine` interface
Added	`DefaultLayoutEngine` implementation
Affected	Custom layout calculations using internal APIs
Fix	Implement `ILayoutEngine` for custom layout behavior.

Target Framework Changes

Dropped Frameworks

Impact: High — if targeting dropped frameworks.

Framework	Status
.NET Framework 4.0	❌ Removed
.NET Framework 4.5.2	❌ Removed
.NET Core 3.0 / 3.1	❌ Removed
.NET 5.0	❌ Removed
.NET 6.0 / 7.0 / 8.0	❌ Not targeted

Supported frameworks in v5.0.0:

.NET Framework 4.8
.NET 9.0 (with -windows TFM)
.NET 10.0 (with -windows TFM)

Fix: Update your project to target one of the supported frameworks:

<!-- .NET 9 -->
<TargetFramework>net9.0-windows</TargetFramework>

<!-- .NET 10 -->
<TargetFramework>net10.0-windows</TargetFramework>

<!-- .NET Framework 4.8 -->
<TargetFramework>net48</TargetFramework>

<!-- Multi-target -->
<TargetFrameworks>net10.0-windows;net9.0-windows;net48</TargetFrameworks>

New Features (Non-Breaking)

These additions are new in v5.0.0 and do not break existing code:

Feature	Package	Description
ToggleDockingManager	`AvalonDock`	VS Code / Rider-style sidebar with toggle buttons.
Arc Theme	`AvalonDock.Themes.Arc`	Modern theme with dark/light variants.
JSON Serializer	`AvalonDock.Serializer.Json`	JSON-based layout serialization.
MVVM Base Classes	`AvalonDock.Mvvm`	`DockableBase`, `ToolboxBase`, `DockLayoutService`, etc.
MVVM CommunityToolkit	`AvalonDock.Mvvm.CommunityToolkit`	`ObservableDockableBase`, `ObservableToolboxBase` with source generators.
DI Integration	`AvalonDock.DependencyInjection`	`AddAvalonDock()` extension method.
Core Abstractions	`AvalonDock.Core`	`IFactory`, `IDockingManager`, `IAutoHideManager`, etc.
DTO Serialization	`AvalonDock.Core`	Serialization refactored to DTO layer; custom serializers can extend `LayoutSerializerBase`.

Behavioral Changes

Layout Restacking

A bug fix in v5.0.0 corrects the restacking behavior for bottom-docked panels. If your application relied on the previous (incorrect) behavior, you may notice panels appearing in different positions after restacking.

Fix: Test your layouts and adjust panel placement if needed.

Summary Table

Category	Change	Impact	Action
Packages	Serializers separated	High	Install serializer package
Namespaces	Serializer namespace moved	High	Update `using` statements
Architecture	`ILayoutEngine` added	Low	No action for default behavior
Frameworks	.NET < 4.8 dropped	High	Upgrade target framework
Frameworks	.NET Core 3.x / 5 dropped	High	Upgrade target framework
Themes	Arc theme added	None	Optional adoption
Serialization	JSON serializer added	None	Optional adoption
Behavior	Bottom restack fix	Low	Test and verify layouts