luidones

internal static T AddedOrSingleOrDefault<T>(this IDbSet<T> source, DbContext context, Func<T, bool> comparer)
     where T : class
{
    T result = null;

    var entry = context.ChangeTracker.Entries<T>()
        .SingleOrDefault(e => e.State == EntityState.Added && comparer(e.Entity));

    if (entry != null)
        result = entry.Entity;