c# Directory

        public static void TestDirectory()
        {
            string dir = @"D:\FileTest";
            if (Directory.Exists(dir))
            {
                try
                {
                    Console.WriteLine("-----------EnumerateFileSystemEntries------------");
                    var entries = Directory.EnumerateFileSystemEntries(dir,"*.*",SearchOption.AllDirectories);
                    foreach (var e in entries)  //在此行加断点可以发现，尽管dir中有大量文件，EnumerateFileSystemEntries依然直接返回。
                    {
                        Console.WriteLine(e.ToString());//直到真正使用entries时，才进行枚举。
                    }
                    Console.WriteLine("-----------------------");

                    Console.WriteLine("-----------EnumerateDirectories------------");
                    var dirs = Directory.EnumerateDirectories(dir, "*.*", SearchOption.AllDirectories);
                    foreach (var d in dirs)
                    {
                        Console.WriteLine(d.ToString());
                    }
                    Console.WriteLine("-----------------------");

                    Console.WriteLine("-----------EnumerateFiles------------");
                    var files = Directory.EnumerateFiles(dir,"*.txt",SearchOption.AllDirectories);
                    foreach (var f in files)
                    {
                        Console.WriteLine(f.ToString());
                    }
                    Console.WriteLine("-----------------------");
                }
                catch (Exception ex)
                {
                    Console.WriteLine(ex.ToString());
                }
            }
        }