# System.Text.Json.Serialization

``` diff
 namespace System.Text.Json.Serialization {
+    public sealed class JsonConstructorAttribute : JsonAttribute {
+        public JsonConstructorAttribute();
+    }
     public sealed class JsonIgnoreAttribute : JsonAttribute {
+        public JsonIgnoreCondition Condition { get; set; }
     }
+    public enum JsonIgnoreCondition {
+        Always = 0,
+        Never = 2,
+        WhenNull = 1,
+    }
+    public sealed class JsonIncludeAttribute : JsonAttribute {
+        public JsonIncludeAttribute();
+    }
+    public sealed class ReferenceHandling {
+        public static ReferenceHandling Default { get; }
+        public static ReferenceHandling Preserve { get; }
+    }
 }
```

