# System.Runtime.InteropServices

``` diff
 namespace System.Runtime.InteropServices {
     public static class CollectionsMarshal {
+        public static ref TValue? GetValueRefOrAddDefault<TKey, TValue, TAlternateKey>(Dictionary.AlternateLookup<TAlternateKey> dictionary, TAlternateKey key, out bool exists);
+        public static ref TValue GetValueRefOrNullRef<TKey, TValue, TAlternateKey>(Dictionary.AlternateLookup<TAlternateKey> dictionary, TAlternateKey key);
     }
 }
```

