Add AvalonDock as submodule for the time being.

.gitmodules

@@ -1,4 +1,7 @@
 [submodule "ILSpy-tests"]
 	path = ILSpy-tests
 	url = https://github.com/icsharpcode/ILSpy-tests
-   
+   
+[submodule "AvalonDock"]
+	path = AvalonDock
+	url = https://github.com/siegfriedpammer/AvalonDock

AvalonDock

@@ -0,0 +1 @@
+Subproject commit e5ec95d624d5c3e6998832c4d8adefdaf11fd9c8

ILSpy.sln

@@ -33,6 +33,8 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "ICSharpCode.Decompiler.PdbP
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "ILSpy.Tests", "ILSpy.Tests\ILSpy.Tests.csproj", "{B51C6636-B8D1-4200-9869-08F2689DE6C2}"
 EndProject
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Xceed.Wpf.AvalonDock", "AvalonDock\source\Components\Xceed.Wpf.AvalonDock\Xceed.Wpf.AvalonDock.csproj", "{D87D783A-A8EE-4A36-AAED-3AB21DC98046}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -79,6 +81,10 @@ Global
 		{B51C6636-B8D1-4200-9869-08F2689DE6C2}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{B51C6636-B8D1-4200-9869-08F2689DE6C2}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{B51C6636-B8D1-4200-9869-08F2689DE6C2}.Release|Any CPU.Build.0 = Release|Any CPU
+		{D87D783A-A8EE-4A36-AAED-3AB21DC98046}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{D87D783A-A8EE-4A36-AAED-3AB21DC98046}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{D87D783A-A8EE-4A36-AAED-3AB21DC98046}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{D87D783A-A8EE-4A36-AAED-3AB21DC98046}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE

ILSpy/ILSpy.csproj

@@ -50,7 +50,6 @@
 
   <ItemGroup>
     <PackageReference Include="AvalonEdit" Version="6.0.0" />
-    <PackageReference Include="Dirkster.AvalonDock" Version="3.6.1" />
     <PackageReference Include="Microsoft.VisualStudio.Composition" Version="16.3.7" />
     <PackageReference Include="System.Composition" Version="1.3.0" />
     <PackageReference Include="Mono.Cecil" Version="0.10.3" />
@@ -60,6 +59,7 @@
   <ItemGroup>
     <ProjectReference Include="..\ICSharpCode.Decompiler\ICSharpCode.Decompiler.csproj" />
     <ProjectReference Include="..\SharpTreeView\ICSharpCode.TreeView.csproj" />
+    <ProjectReference Include="..\AvalonDock\source\Components\Xceed.Wpf.AvalonDock\Xceed.Wpf.AvalonDock.csproj" />
   </ItemGroup>
 
   <ItemGroup Condition="'$(Configuration)' == 'Debug'">