用c#创建一个下拉列表

我是新的编程，我想一些帮助我如何创建一个下拉列表的通过/失败在c#。如有任何帮助，不胜感激

class Program
{
    static void Main(string[] args)
    {
        Match match;
        string pattern = @"'s*#'sfeatures+.+|'s*#'scalabash+.+";
        string replacement = " Step #... ";
        string result;

        // Read input file
        StreamReader inFile = new StreamReader(@"C:'Users'Desktop'file.txt");
        string input = inFile.ReadToEnd();
        inFile.Close();
        // matching pattern
        match = Regex.Match(input, pattern, RegexOptions.Multiline);
        while (match.Success)
        {
            // Console.WriteLine("'{0}'character found: {1} ", match.Value, match.Index);
            match = match.NextMatch();
        }
        // replace
        result = Regex.Replace(input, pattern, replacement);
        // Console.WriteLine(result);
        File.WriteAllText(@"C:'Users'Desktop'file.txt", result);