SelectExcept.cs

public static IQueryable<T> SelectExcept<T, TKey>(this IQueryable<T> sequence,
    Expression<Func<T, TKey>> excluder) where T : new()
{
    List<string> excludedProperties = new List<string>();
    if (excluder.Body is MemberExpression memberExpression)
    {
        excludedProperties.Add(memberExpression.Member.Name);
    }
    else if (excluder.Body is NewExpression anonymousExpression)
    {
        excludedProperties.AddRange(anonymousExpression.Members.Select(m => m.Name));
    }
    var includedProperties = typeof(T).GetProperties()
        .Where(p => !excludedProperties.Contains(p.Name));

    return sequence.Select(x => Selector(x, includedProperties));
}

private static T Selector<T>(T obj, IEnumerable<PropertyInfo> properties)
{
    var instance = Activator.CreateInstance<T>();
    foreach (var property in properties)
        property.SetValue(instance, property.GetValue(obj), null);

    return instance;
}