MethodExtention_LogCollection

public static string Log<T> (this IEnumerable<T> collection) => Log (collection, i => i);

public static string Log<T, TResult> (this IEnumerable<T> collection, System.Func<T, TResult> selector, string Format = "{0}", string separator = "\n")
{
    string result = "";
    result = collection != null ? collection.Count ().ToString () : "Null";
    result += " items {0}\n------\n".AsFormat (typeof (T).Name)
    foreach (var item in collection.Select (selector))
    {
        var parameters = new object[] { item };
        result += string.Format (Format + separator, parameters);
    }
    return result;
}