How to return null if a String is null or Empty in C#

        /// <summary>Returns null if <paramref name="self" /> is <see cref="String.IsNullOrEmpty" />.</summary>
        /// <param name="self"></param>
        /// <returns></returns>
        [CanBeNull]
        [DebuggerStepThrough]
        [Pure]
        public static String? NullIfEmpty( [CanBeNull] this String? self ) => String.IsNullOrEmpty( self ) ? null : self;


How to Trim whitespace from a String in C#

        /// <summary>Trim the ToString() of the object; returning null if null, empty, or whitespace.</summary>
        /// <param name="self"></param>
        /// <returns></returns>
        [DebuggerStepThrough]
        [CanBeNull]
        [Pure]
        public static String? Trimmed<T>( [CanBeNull] this T self ) =>
            self switch {
                null => default( String? ),
                String s => s.Trim().NullIfEmpty(),
                var _ => self.ToString()?.Trim().NullIfEmpty()
            };