# System.Collections.Generic

``` diff
 namespace System.Collections.Generic {
     public static class CollectionExtensions {
+        public static ReadOnlyCollection<T> AsReadOnly<T>(this IList<T> list);
+        public static ReadOnlyDictionary<TKey, TValue> AsReadOnly<TKey, TValue>(this IDictionary<TKey, TValue> dictionary);
     }
     public class SortedList<TKey, TValue> : ICollection, ICollection<KeyValuePair<TKey, TValue>>, IDictionary, IDictionary<TKey, TValue>, IEnumerable, IEnumerable<KeyValuePair<TKey, TValue>>, IReadOnlyCollection<KeyValuePair<TKey, TValue>>, IReadOnlyDictionary<TKey, TValue> {
+        public TKey GetKeyAtIndex(int index);
+        public TValue GetValueAtIndex(int index);
+        public void SetValueAtIndex(int index, TValue value);
     }
 }
```

