public static int CountEx <TSource>(this IEnumerable <TSource> source, Func <TSource, bool> predicate)
 {
     return(source.AnyEx() ? source.Count(predicate) : 0);
 }
 public static int CountEx <TSource>(this IEnumerable <TSource> source)
 {
     return(source.AnyEx() ? source.Count() : 0);
 }