public static List <TKey> ToList <TKey, TValue>(this SortedDictionary <TKey, TValue> .KeyCollection source)
 => ValueReadOnlyCollectionExtensions.ToList <ValueWrapper <TKey, TValue>, SortedDictionary <TKey, TValue> .KeyCollection.Enumerator, TKey>(new ValueWrapper <TKey, TValue>(source));
 public static List <KeyValuePair <TKey, TValue> > ToList <TKey, TValue>(this Dictionary <TKey, TValue> source)
     where TKey : notnull
 => ValueReadOnlyCollectionExtensions.ToList <ValueWrapper <TKey, TValue>, Dictionary <TKey, TValue> .Enumerator, KeyValuePair <TKey, TValue> >(new ValueWrapper <TKey, TValue>(source));
 public static List <TValue> ToList <TKey, TValue>(this SortedDictionary <TKey, TValue> .ValueCollection source)
     where TKey : notnull
 => ValueReadOnlyCollectionExtensions.ToList <ValueWrapper <TKey, TValue>, SortedDictionary <TKey, TValue> .ValueCollection.Enumerator, TValue>(new ValueWrapper <TKey, TValue>(source));