其实代码demo很简洁，只是逻辑有点绕，主要是要一层一层调用自己，要清楚当前是第几层调用，及递归调用时进的点和出的点在哪儿，一切就清晰明了了。

        /// <summary>
        /// 删除指定目录下面的所有文件和文件夹
        /// </summary>
        /// <param name="path"></param>
        /// <param name="level"></param>
        /// <param name="isFirstCall"></param>
        static void DeleteAllFilesAndFolders(string path,int level,bool isFirstCall)
        {
            level++;
            Console.WriteLine($"Current Level:{level},Current Directory:{path}");

            //删除当前目录下的所有文件
            string[] files = Directory.GetFiles(path);
            foreach (var file in files)
            {
                File.Delete(file);
            }

            //判断当前目录是否存在子目录
            if(Directory.GetDirectories(path).Length != 0)
            {
                string[] dirs = Directory.GetDirectories(path);
                for (int i = 0; i < dirs.Length; i++)
                {
                    DeleteAllFilesAndFolders(dirs[i], level,false);
                }
            }

            //删除当前目录,只保留传进来的根目录
            if (!isFirstCall)
            {
                Directory.Delete(path);
                Console.WriteLine($"已删除Level{level}目录:{path}");
            }
        }

        /// <summary>
        /// 将源路径下的所有文件和文件夹全部复制到目标文件夹中
        /// </summary>
        /// <param name="sourceDirectory"></param>
        /// <param name="DestinationDirectory"></param>
        /// <param name="level"></param>
        static void CopyAllFilesAndFolders(string sourceDirectory,string DestinationDirectory,int level = 0)
        {
            level++;
            Console.WriteLine($"Current Level: {level}");
            Console.WriteLine($"Current Source Directory: {sourceDirectory}");
            Console.WriteLine($"Current Destination Directory: {DestinationDirectory}");
            //将源目录下的文件复制到目标目录下
            string[] sourceFilePaths = Directory.GetFiles(sourceDirectory);
            string sourceFileName = null;
            foreach (string sourceFilePath in sourceFilePaths)
            {
                sourceFileName = Path.GetFileName(sourceFilePath);
                File.Copy(sourceFilePath, DestinationDirectory + "\\"+ sourceFileName);
            }
            
            //从源头目录中获取其子目录
            string[] dirs = Directory.GetDirectories(sourceDirectory);
            string TargetDirectory = null;
            if (dirs.Length !=0)
            {
                //在目标目录中创建子目录
                for (int i = 0; i < dirs.Length; i++)
                {
                    string[] dir_splited = dirs[i].Split('\\');
                    //TargetDirectory = dirs[i].Replace(sourceDirectory, DestinationDirectory);
                    TargetDirectory = DestinationDirectory + "\\" + dir_splited[dir_splited.Length - 1];
                    Directory.CreateDirectory(TargetDirectory);
                    CopyAllFilesAndFolders(dirs[i], TargetDirectory,level);
                }
            }
        }

private void CSV2List_Load(object sender, EventArgs e)
{
    string sourceDirectory = @"D:\Test";
    string targetDirectory = @"D:\Target";

    //删除指定目录下的所有文件和文件夹
    DeleteAllFilesAndFolders(targetDirectory, 0, true);
    MessageBox.Show("Cleared");
    CopyAllFilesAndFolders(sourceDirectory, targetDirectory,0);
    MessageBox.Show("Copied");
}

代码执行的控制台输出如下：

运行程序，先清楚目标目录下的所有文件和文件夹，然后将源目录D:\Test下的所有文件和子目录都被复制到D:\Target目录下。