WinForm(C#)复制文件夹

如:我想将 C:\abc文件夹复制到 D:\ 下面怎么办呀?

using System.IO; 

 /// <summary>
        /// 拷贝文件夹
        /// </summary>
        /// <param name="srcdir"></param>
        /// <param name="desdir"></param>
        private void CopyDirectory(string srcdir, string desdir)
        {
            string folderName = srcdir.Substring(srcdir.LastIndexOf("\\")+1);

            string desfolderdir = desdir +"\\"+ folderName;

            if (desdir.LastIndexOf("\\") == (desdir.Length - 1))
            {
                desfolderdir = desdir + folderName;
            }
            string[] filenames = Directory.GetFileSystemEntries(srcdir);

            foreach (string file in filenames)// 遍历所有的文件和目录
            {
                if (Directory.Exists(file))// 先当作目录处理如果存在这个目录就递归Copy该目录下面的文件
                {

                    string currentdir = desfolderdir + "\\" + file.Substring(file.LastIndexOf("\\") + 1);
                    if (!Directory.Exists(currentdir))
                    {
                        Directory.CreateDirectory(currentdir);
                    }

                    CopyDirectory(file, desfolderdir);
                }

                else // 否则直接copy文件
                {
                    string srcfileName = file.Substring(file.LastIndexOf("\\")+1);

                    srcfileName = desfolderdir + "\\" + srcfileName;


                    if (!Directory.Exists(desfolderdir))
                    {
                        Directory.CreateDirectory(desfolderdir);
                    }
                    
                    
                    File.Copy(file, srcfileName);
                }
            }//foreach 

}//function end