qdr.app.studiou.orders2printpack/Extensions/StringExt.cs

namespace qdr.app.studiou.orders2printpack.Extensions
{
    public static class StringExt
    {
        public static string ToQuotedString(this string str)
        {
            if (str == null)
                return string.Empty;
            return ToDecoratedString(str, "\"");
        }

        public static string ToDecoratedString(this string str, string leftDecoration, string rightDecoration)
        {
            if (str == null)
                return string.Empty;
            return leftDecoration + str + rightDecoration;
        }

        public static string ToDecoratedString(this string str, string bothDecoration)
        {
            if (str == null)
                return string.Empty;
            return ToDecoratedString(str, bothDecoration, bothDecoration);
        }


        /// <summary>
        /// Returns a list of all duplicate string items in a collection.
        /// </summary>
        /// <param name="source">The source collection to check for duplicates.</param>
        /// <returns>An IEnumerable containing only the duplicate items.</returns>
        public static IEnumerable<string> GetDuplicates(this IEnumerable<string> source)
        {
            if (source == null)
                throw new ArgumentNullException(nameof(source));

            return source
                .GroupBy(x => x)
                .Where(g => g.Count() > 1)
                .Select(g => g.Key);
        }


    }
}