/// <summary>
/// set the item count
/// </summary>
/// <param name="item"></param>
/// <param name="newCountFunc">current item count to new count value</param>
/// <returns></returns>
private int SetItemCount(TValue item, Func <int, int> newCountFunc)
{
int newItemCount;
int oldItemCount;
NullableKey <TValue> key = new NullableKey <TValue>(item);
if (_values.TryGetValue(key, out int currentItemCount))
{
oldItemCount = currentItemCount;
newItemCount = newCountFunc(currentItemCount);
}
else
{
oldItemCount = 0;
newItemCount = newCountFunc(0);
}
if (oldItemCount != newItemCount)
{
if (newItemCount == 0)
{
_values.Remove(key);
}
else
{
_values[key] = newItemCount;
}
Count = Count - oldItemCount + newItemCount;
}
return(oldItemCount);
}
public bool Equals(NullableKey <TKey> other) => Equals(Key, other.Key);