EntityRelationshipMap

gistfile1.txt

public static void EntityRelationshipMap<T, K>(this ICollection<T> startingCollection, ICollection<T> newCollection,
                                Func<T, K> selector )
{
    var newItemCompareValues = newCollection.Select(selector);
    var existingItemCompareValues = startingCollection.Select(selector);

    var alternativeTitlesToRemove = startingCollection.Where(at => !newItemCompareValues.Contains(selector(at)));
    var alternativeTitlesToAdd = newCollection.Where(at => !existingItemCompareValues.Contains(selector(at)));

    foreach (var alternativeTitleToRemove in alternativeTitlesToRemove)
    {
        startingCollection.Remove(alternativeTitleToRemove);
    }

    foreach (var alternativeTitleToAdd in alternativeTitlesToAdd)
    {
        startingCollection.Add(alternativeTitleToAdd);
    }
}