private void Initialize(IEqualityComparer <TKey> comparer = null)
{
this.Comparer = comparer;
if (comparer != null)
{
_keyedCollection = new KeyedCollection2 <TKey, KeyValuePair <TKey, TValue> >(x => x.Key, comparer);
}
else
{
_keyedCollection = new KeyedCollection2 <TKey, KeyValuePair <TKey, TValue> >(x => x.Key);
}
}