Or IsEmptyOrContains to be consistent with current methods.

>I guess you're right. It would me more consistent with other String methods. TBH I don't really like either in that they are not truly descriptive of what the method does :-{
>
>Maybe swap it around :

public static bool IsEmptyOrIn(this String str, string longsString)
>        {
>            return string.IsNullOrEmpty(str) || longsString.Contains(str);
>        }
>       // with
>      var x = ShortString.IsEmptyOrIn(LongString);

>