From 4d6a4da02acaa6b94fddeb3e212ea125ad550174 Mon Sep 17 00:00:00 2001
From: Curtis Wensley <curtis.wensley@gmail.com>
Date: Tue, 1 Aug 2023 13:25:39 -0700
Subject: [PATCH] Fix serializing objects with custom child types using
 DataObject/Clipboard

---
 src/Eto/Forms/ObjectData.cs                   | 33 +++++++++++++++++--
 .../UnitTests/Forms/ClipboardTests.cs         | 10 ++++++
 2 files changed, 41 insertions(+), 2 deletions(-)

diff --git a/src/Eto/Forms/ObjectData.cs b/src/Eto/Forms/ObjectData.cs
index f751a42ac..a7fb1c9cf 100755
--- a/src/Eto/Forms/ObjectData.cs
+++ b/src/Eto/Forms/ObjectData.cs
@@ -26,7 +26,7 @@ internal static byte[] Serialize(object value, Type baseType)
 
 		using (var ms = new MemoryStream())
 		{
-			var serializer = new DataContractSerializer(typeof(ObjectData), new [] { baseType });
+			var serializer = new DataContractSerializer(typeof(ObjectData), GetKnownTypes(baseType));
 			serializer.WriteObject(ms, data);
 			
 			// for debugging
@@ -35,6 +35,34 @@ internal static byte[] Serialize(object value, Type baseType)
 			return ms.ToArray();
 		}
 	}
+	
+	static IEnumerable<Type> GetKnownTypes(Type baseType)
+	{
+		yield return baseType;
+		
+		// DataContracts must specify their types explicitly using the KnownTypeAttribute
+		var isDataContract = baseType.GetCustomAttribute<DataContractAttribute>() != null;
+		if (isDataContract)
+			yield break;
+			
+		var knownTypes = new HashSet<Type>();
+		
+		foreach (var field in FormatterServices.GetSerializableMembers(baseType))
+		{
+			var type = field switch
+			{
+				PropertyInfo pi => pi.PropertyType,
+				FieldInfo fi => fi.FieldType,
+				_ => null
+			};
+			if (!knownTypes.Contains(type))
+			{
+				yield return type;
+				knownTypes.Add(type);
+			}
+		}
+	}
+	
 
 	internal static object Deserialize(Stream stream, Type objectType)
 	{
@@ -73,7 +101,8 @@ internal static object Deserialize(Stream stream, Type objectType)
 		{
 			// read again, but with known type populated
 			stream.Position = 0;
-			var serializer = new DataContractSerializer(typeof(ObjectData), new[] { objectType });
+			
+			var serializer = new DataContractSerializer(typeof(ObjectData), GetKnownTypes(objectType));
 			var data = serializer.ReadObject(stream) as ObjectData;
 
 			ms?.Dispose();
diff --git a/test/Eto.Test/UnitTests/Forms/ClipboardTests.cs b/test/Eto.Test/UnitTests/Forms/ClipboardTests.cs
index 451c4e6e9..b76fd81f5 100755
--- a/test/Eto.Test/UnitTests/Forms/ClipboardTests.cs
+++ b/test/Eto.Test/UnitTests/Forms/ClipboardTests.cs
@@ -61,6 +61,7 @@ public class SerializableObject : ISerializable
 		{
 			
 			public string SomeValue { get; set; }
+			public ChildObject ChildObject { get; set; } = new ChildObject();
 			public SerializableObject()
 			{
 			}
@@ -68,11 +69,13 @@ public SerializableObject()
 			public SerializableObject(SerializationInfo info, StreamingContext context)
 			{
 				SomeValue = info.GetString("SomeValue");
+				ChildObject = info.GetValue("Child", typeof(ChildObject)) as ChildObject;
 			}
 			
 			public void GetObjectData(SerializationInfo info, StreamingContext context)
 			{
 				info.AddValue("SomeValue", SomeValue);
+				info.AddValue("Child", ChildObject);
 			}
 		}
 		
@@ -80,6 +83,13 @@ public void GetObjectData(SerializationInfo info, StreamingContext context)
 		public class SomeOtherObject
 		{
 			public string SomeValue { get; set; }
+
+			public ChildObject ChildObject { get; set; } = new ChildObject();
+		}
+		
+		public class ChildObject
+		{
+			public bool SomeProperty { get; set; } = new Random().Next() % 2 == 0;
 		}
 
 		static byte[] SampleByteData => new byte[] { 10, 20, 30 };