问使用StartsWith C#的过滤器列表

EN

        static void Main(string[] args)
        {
            StreamReader objReader = new StreamReader(
                @"C:\Users\thoma\Documents\Visual Studio 2019\Backup Files\data.txt");



            string orden = "";
            List<string> arrText = new List<string>();

            while (orden != null)
            {
                orden = objReader.ReadLine();
                if (orden != null) arrText.Add(orden);
            }
            objReader.Close();

           foreach (string sOutput in arrText)
                Console.WriteLine(sOutput);

            Console.WriteLine("Order alphabetically ascending press 'a': ");
            Console.WriteLine("Ordener descendant alphabetical press 'b': ");                       

            instruccion = Console.ReadLine();
            if (instruccion == "a"){
                var resultList = arrText.Where(o => o.StartsWith("r"));
                Console.WriteLine(resultList);    
//string ascending = string.Format("{0}{1}{0}", "'", string.Join("','", arrText.OrderBy(x => x)));


            }         
            Console.ReadLine();
        }
    }
}