elvisgs

public static TSource MaxOrDefault<TSource>(this IEnumerable<TSource> source)
    where TSource : IComparable
{
    return source.MaxOrDefault(default(TSource));
}

public static TSource MaxOrDefault<TSource>(this IEnumerable<TSource> source, TSource defaultValue)
    where TSource : IComparable
{
    return source.Aggregate(defaultValue, (a, b) => a != null && a.CompareTo(b) > 0 ? a : b);