Do not require matching ctor, if top level element

src/Markup/Avalonia.Markup.Xaml.Loader/AvaloniaXamlIlRuntimeCompiler.cs

@@ -234,7 +234,7 @@ namespace Avalonia.Markup.Xaml.XamlIl
                 parsedDocuments.Add(new XamlDocumentResource(parsed, document.BaseUri?.ToString(), null, null,
                     builder,
                     compiler.DefinePopulateMethod(builder, parsed, AvaloniaXamlIlCompiler.PopulateName, true),
-                    compiler.DefineBuildMethod(builder, parsed, AvaloniaXamlIlCompiler.BuildName, true)));
+                    document.RootInstance is null ? compiler.DefineBuildMethod(builder, parsed, AvaloniaXamlIlCompiler.BuildName, true) : null));
                 originalDocuments.Add(document);
             }
 

src/Markup/Avalonia.Markup.Xaml.Loader/xamlil.github

@@ -1 +1 @@
-Subproject commit 491de981dd4433ee58bc9540e2cd4a5d168f8168
+Subproject commit b800d3e1fac0940c571bfa540e3af4dbd59f7dbb

tests/Avalonia.Markup.Xaml.UnitTests/Xaml/BasicTests.cs

@@ -899,6 +899,17 @@ namespace Avalonia.Markup.Xaml.UnitTests.Xaml
             Assert.Equal("Foo", target.Text);
         }
 
+        [Fact]
+        public void Should_Parse_And_Populate_Type_Without_Public_Ctor()
+        {
+            var xaml = @"<ObjectWithoutPublicCtor xmlns='clr-namespace:Avalonia.Markup.Xaml.UnitTests.Xaml' Test2='World' />";
+            var target = (ObjectWithoutPublicCtor)AvaloniaRuntimeXamlLoader.Load(xaml, rootInstance: new ObjectWithoutPublicCtor("Hello"));
+
+            Assert.NotNull(target);
+            Assert.Equal("World", target.Test2);
+            Assert.Equal("Hello", target.Test1);
+        }
+        
         private class SelectedItemsViewModel : INotifyPropertyChanged
         {
             public string[] Items { get; set; }
@@ -928,6 +939,18 @@ namespace Avalonia.Markup.Xaml.UnitTests.Xaml
             Child = child;
         }
     }
+    
+    public class ObjectWithoutPublicCtor
+    {
+        public ObjectWithoutPublicCtor(string param)
+        {
+            Test1 = param;
+        }
+        
+        public string Test1 { get; set; }
+        
+        public string Test2 { get; set; }
+    }
 
     public class ObjectWithAddChildOfT : IAddChild, IAddChild<string>
     {