public void ChooseDocument(string fileName) { string format = fileName.Substring(fileName.Length - 4); switch (format.ToLower()) { case ".txt": handler = new TXTHandler(fileName); break; case ".doc": handler = new DOCHandler(fileName); break; case ".xml": handler = new XMLHandler(fileName); break; default: Console.WriteLine("Неопознаный формат"); break; } }