public static TSource FirstOrDefault <TSource>(this SortedSet <TSource> source) => ValueReadOnlyCollection.FirstOrDefault <ValueWrapper <TSource>, SortedSet <TSource> .Enumerator, TSource>(new ValueWrapper <TSource>(source));
public static TKey FirstOrDefault <TKey, TValue>(this SortedDictionary <TKey, TValue> .KeyCollection source) => ValueReadOnlyCollection.FirstOrDefault <ValueWrapper <TKey, TValue>, SortedDictionary <TKey, TValue> .KeyCollection.Enumerator, TKey>(new ValueWrapper <TKey, TValue>(source));
public static KeyValuePair <TKey, TValue> FirstOrDefault <TKey, TValue>(this SortedDictionary <TKey, TValue> source) => ValueReadOnlyCollection.FirstOrDefault <ValueWrapper <TKey, TValue>, SortedDictionary <TKey, TValue> .Enumerator, KeyValuePair <TKey, TValue> >(new ValueWrapper <TKey, TValue>(source));
public static TValue FirstOrDefault <TKey, TValue>(this Dictionary <TKey, TValue> .ValueCollection source) => ValueReadOnlyCollection.FirstOrDefault <ValueWrapper <TKey, TValue>, Dictionary <TKey, TValue> .ValueCollection.Enumerator, TValue>(new ValueWrapper <TKey, TValue>(source));