namespace System.Collections.Concurrent
{
    [DebuggerDisplay("Count = {Count}")]
    [DebuggerTypeProxy(typeof(IDictionaryDebugView<?, ?>))]
    [DefaultMember("Item")]
    public class ConcurrentDictionary<TKey, TValue> : ICollection<KeyValuePair<TKey, TValue>>, IDictionary<TKey, TValue>, IEnumerable, IEnumerable<KeyValuePair<TKey, TValue>>, IReadOnlyCollection<KeyValuePair<TKey, TValue>>, IReadOnlyDictionary<TKey, TValue>, ICollection, IDictionary
    {
        public TValue GetOrAdd<TArg>(TKey key, Func<TKey, TArg, TValue> valueFactory, TArg factoryArgument);
    }
}