DIFFÉRENTIELLE ENTRE DEUX COLLECTION

// IPrimaryKey :

public interface IPrimaryKey
{
    int PrimaryKeyValue{get;}
}

// Extention :

public static class EnumerableExtention
{

    private static List<int> GetIds(IEnumerable<IPrimaryKey> list)
    {
        if (list == null) return new List<int>();
        return list.Select(it => it.PrimaryKeyValue).ToList();
    }


    public static IEnumerable<T> diffObjectToRemove<T>(this IEnumerable<T> source, IEnumerable<IPrimaryKey> list)
        where T : class, IPrimaryKey
    {
        if (source == null) return new List<T>();
        var listIdsFrom = GetIds(list);
        var listIdsTo = GetIds(source);
        var idsToDelete = listIdsTo.Except(listIdsFrom);
        return source.Where(it => idsToDelete.Contains(it.PrimaryKeyValue)).ToList();
    }

    public static IEnumerable<T> diffObjectToAdd<T>(this IEnumerable<IPrimaryKey> source, IEnumerable<T> list)
        where T : class, IPrimaryKey
    {
        if (list == null) return new List<T>();
        var listIdsFrom = GetIds(list);
        var listIdsTo = GetIds(source);
        var idsToAdd = listIdsFrom.Except(listIdsTo);
        return list.Where(it => idsToAdd.Contains(it.PrimaryKeyValue)).ToList();
    }

    public static IEnumerable<T> diffObjectToUpdate<T>(this IEnumerable<T> source, IEnumerable<IPrimaryKey> list)
        where T : class, IPrimaryKey
    {
        if (source == null) return new List<T>();
        var listIdsFrom = GetIds(list);
        var listIdsTo = GetIds(source);
        var idsToUpdate = listIdsTo.Intersect(listIdsFrom);
        return source.Where(it => idsToUpdate.Contains(it.PrimaryKeyValue)).ToList();
    }
}