Fix #2773: Decompilation of readonly properties in XAML

ILSpy.BamlDecompiler.Tests/BamlTestRunner.cs

@@ -154,6 +154,12 @@ namespace ILSpy.BamlDecompiler.Tests
 			RunTest("cases/issue2116");
 		}
 
+		[Test]
+		public void ReadonlyProperty()
+		{
+			RunTest("cases/readonlyproperty");
+		}
+
 		#region RunTest
 		void RunTest(string name)
 		{

ILSpy.BamlDecompiler.Tests/Cases/MyControl.xaml.cs

@@ -16,6 +16,7 @@
 // OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 // DEALINGS IN THE SOFTWARE.
 
+using System.Collections;
 using System.Windows.Controls;
 
 namespace ILSpy.BamlDecompiler.Tests.Cases
@@ -25,6 +26,8 @@ namespace ILSpy.BamlDecompiler.Tests.Cases
 	/// </summary>
 	public partial class MyControl : UserControl
 	{
+		public IList DataTypes { get; } = new ArrayList();
+
 		public MyControl()
 		{
 			InitializeComponent();

ILSpy.BamlDecompiler.Tests/ILSpy.BamlDecompiler.Tests.csproj

@@ -58,6 +58,7 @@
     <Compile Include="Cases\MyControl.xaml.cs">
       <DependentUpon>MyControl.xaml</DependentUpon>
     </Compile>
+    <Compile Include="Cases\ReadonlyProperty.xaml.cs" />
     <Compile Include="Cases\Resources.xaml.cs">
       <DependentUpon>Resources.xaml</DependentUpon>
     </Compile>
@@ -102,6 +103,9 @@
     <Page Include="Cases\MarkupExtension.xaml" />
     <Page Include="Cases\MyControl.xaml" />
     <Page Include="Cases\NamespacePrefix.xaml" />
+    <Page Include="Cases\ReadonlyProperty.xaml">
+      <Generator>MSBuild:Compile</Generator>
+    </Page>
     <Page Include="Cases\Resources.xaml" />
     <Page Include="Cases\Simple.xaml">
       <CopyToOutputDirectory>Always</CopyToOutputDirectory>

ILSpy.BamlDecompiler/Rewrite/MarkupExtensionRewritePass.cs

@@ -21,9 +21,13 @@
 */
 
 using System.Collections.Generic;
+using System.DirectoryServices.ActiveDirectory;
 using System.Linq;
+using System.Windows.Forms;
 using System.Xml.Linq;
 
+using ICSharpCode.Decompiler.TypeSystem;
+
 using ILSpy.BamlDecompiler.Xaml;
 
 namespace ILSpy.BamlDecompiler.Rewrite
@@ -64,8 +68,15 @@ namespace ILSpy.BamlDecompiler.Rewrite
 		{
 			var type = parent.Annotation<XamlType>();
 			var property = elem.Annotation<XamlProperty>();
-			if ((property == null || type == null) && elem.Name != key)
-				return false;
+
+			if (elem.Name != key)
+			{
+				if (property == null || type == null)
+					return false;
+
+				if (property.ResolvedMember is IProperty { CanSet: false })
+					return false;
+			}
 
 			if (elem.Elements().Count() != 1 || elem.Attributes().Any(t => t.Name.Namespace != XNamespace.Xmlns))
 				return false;