dotnet-core/release-notes/3.0/preview/api-diff/preview6/3.0-preview6_System.Reflection.md

System.Reflection

 namespace System.Reflection {
-    public struct CustomAttributeNamedArgument
+    public readonly struct CustomAttributeNamedArgument
-    public struct CustomAttributeTypedArgument
+    public readonly struct CustomAttributeTypedArgument
     public sealed class ReflectionTypeLoadException : SystemException, ISerializable {
+        public override string Message { get; }
+        public override string ToString();
     }
     public class TypeDelegator : TypeInfo {
+        public override bool IsCollectible { get; }
     }
 }