# System.Collections

``` diff
 namespace System.Collections {
     public sealed class Comparer : IComparer, ISerializable {
-        public void GetObjectData(SerializationInfo info, StreamingContext context);
+        [EditorBrowsableAttribute(EditorBrowsableState.Never)]
+        [ObsoleteAttribute("This API supports obsolete formatter-based serialization. It should not be called or extended by application code.", DiagnosticId="SYSLIB0051", UrlFormat="https://aka.ms/dotnet-warnings/{0}")]
+        public void GetObjectData(SerializationInfo info, StreamingContext context);
     }
     public class Hashtable : ICloneable, ICollection, IDeserializationCallback, IDictionary, IEnumerable, ISerializable {
-        protected Hashtable(SerializationInfo info, StreamingContext context);
+        [EditorBrowsableAttribute(EditorBrowsableState.Never)]
+        [ObsoleteAttribute("This API supports obsolete formatter-based serialization. It should not be called or extended by application code.", DiagnosticId="SYSLIB0051", UrlFormat="https://aka.ms/dotnet-warnings/{0}")]
+        protected Hashtable(SerializationInfo info, StreamingContext context);
-        public virtual void GetObjectData(SerializationInfo info, StreamingContext context);
+        [EditorBrowsableAttribute(EditorBrowsableState.Never)]
+        [ObsoleteAttribute("This API supports obsolete formatter-based serialization. It should not be called or extended by application code.", DiagnosticId="SYSLIB0051", UrlFormat="https://aka.ms/dotnet-warnings/{0}")]
+        public virtual void GetObjectData(SerializationInfo info, StreamingContext context);
     }
 }
```

