c#日期时间格式化

//DateTime dt1 = DateTime.Parse("2021-11-22 15:36:48.678");             DateTime dt1 = DateTime.Parse("2021-01-03 06:07:08.009");             Console.WriteLine("y->" + dt1.ToString("y"));             Console.WriteLine("yy->" + dt1.ToString("yy"));             Console.WriteLine("yyy->" + dt1.ToString("yyy"));             Console.WriteLine("yyyy->" + dt1.ToString("yyyy"));             Console.WriteLine("yyyyy->" + dt1.ToString("yyyyy"));             Console.WriteLine("yyyyyy->" + dt1.ToString("yyyyyy"));             Console.WriteLine("y-MM-dd->" + dt1.ToString("y-MM-dd"));             Console.WriteLine("yy-MM-dd->" + dt1.ToString("yy-MM-dd"));             Console.WriteLine("yyy-MM-dd->" + dt1.ToString("yyy-MM-dd"));             Console.WriteLine("yyyy-MM-dd->" + dt1.ToString("yyyy-MM-dd"));             Console.WriteLine("yyyyy-MM-dd->" + dt1.ToString("yyyyy-MM-dd"));             Console.WriteLine("yyyyyy-MM-dd->" + dt1.ToString("yyyyyy-MM-dd"));             Console.WriteLine("M->" + dt1.ToString("M"));             Console.WriteLine("MM->" + dt1.ToString("MM"));             Console.WriteLine("MMM->" + dt1.ToString("MMM"));             Console.WriteLine("MMMM->" + dt1.ToString("MMMM"));             Console.WriteLine("MMMMM->" + dt1.ToString("MMMMM"));             Console.WriteLine("yyyy-M-dd->" + dt1.ToString("yyyy-M-dd"));             Console.WriteLine("yyyy-MM-dd->" + dt1.ToString("yyyy-MM-dd"));             Console.WriteLine("yyyy-MMM-dd->" + dt1.ToString("yyyy-MMM-dd"));             Console.WriteLine("yyyy-MMMM-dd->" + dt1.ToString("yyyy-MMMM-dd"));             Console.WriteLine("yyyy-MMMMM-dd->" + dt1.ToString("yyyy-MMMMM-dd"));             Console.WriteLine("d->" + dt1.ToString("d"));             Console.WriteLine("dd->" + dt1.ToString("dd"));             Console.WriteLine("ddd->" + dt1.ToString("ddd"));             Console.WriteLine("dddd->" + dt1.ToString("dddd"));             Console.WriteLine("ddddd->" + dt1.ToString("ddddd"));             Console.WriteLine("yyyy-MM-d->" + dt1.ToString("yyyy-MM-d"));             Console.WriteLine("yyyy-MM-dd->" + dt1.ToString("yyyy-MM-dd"));             Console.WriteLine("yyyy-MM-ddd->" + dt1.ToString("yyyy-MM-ddd"));             Console.WriteLine("yyyy-MM-dddd->" + dt1.ToString("yyyy-MM-dddd"));             Console.WriteLine("yyyy-MM-ddddd->" + dt1.ToString("yyyy-MM-ddddd"));             Console.WriteLine("hh->" + dt1.ToString("hh"));             Console.WriteLine("hhh->" + dt1.ToString("hhh"));             Console.WriteLine("hhhh->" + dt1.ToString("hhhh"));             Console.WriteLine("h:mm:ss.fff->" + dt1.ToString("h:mm:ss.fff"));             Console.WriteLine("hh:mm:ss.fff->" + dt1.ToString("hh:mm:ss.fff"));             Console.WriteLine("hhh:mm:ss.fff->" + dt1.ToString("hhh:mm:ss.fff"));             Console.WriteLine("hhhh:mm:ss.fff->" + dt1.ToString("hhhh:mm:ss.fff"));             Console.WriteLine("HH->" + dt1.ToString("HH"));             Console.WriteLine("HHH->" + dt1.ToString("HHH"));             Console.WriteLine("HHHH->" + dt1.ToString("HHHH"));             Console.WriteLine("H:mm:ss.fff->" + dt1.ToString("H:mm:ss.fff"));             Console.WriteLine("HH:mm:ss.fff->" + dt1.ToString("HH:mm:ss.fff"));             Console.WriteLine("HHH:mm:ss.fff->" + dt1.ToString("HHH:mm:ss.fff"));             Console.WriteLine("HHHH:mm:ss.fff->" + dt1.ToString("HHHH:mm:ss.fff"));             Console.WriteLine("m->" + dt1.ToString("m"));             Console.WriteLine("mm->" + dt1.ToString("mm"));             Console.WriteLine("mmm->" + dt1.ToString("mmm"));             Console.WriteLine("mmmm->" + dt1.ToString("mmmm"));             Console.WriteLine("HH:m:ss.fff->" + dt1.ToString("HH:m:ss.fff"));             Console.WriteLine("HH:mm:ss.fff->" + dt1.ToString("HH:mm:ss.fff"));             Console.WriteLine("HH:mmm:ss.fff->" + dt1.ToString("HH:mmm:ss.fff"));             Console.WriteLine("HH:mmmm:ss.fff->" + dt1.ToString("HH:mmmm:ss.fff"));             Console.WriteLine("s->" + dt1.ToString("s"));             Console.WriteLine("ss->" + dt1.ToString("ss"));             Console.WriteLine("sss->" + dt1.ToString("sss"));             Console.WriteLine("ssss->" + dt1.ToString("ssss"));             Console.WriteLine("HH:mm:s.fff->" + dt1.ToString("HH:mm:s.fff"));             Console.WriteLine("HH:mm:ss.fff->" + dt1.ToString("HH:mm:ss.fff"));             Console.WriteLine("HH:mm:sss.fff->" + dt1.ToString("HH:mm:sss.fff"));             Console.WriteLine("HH:mm:ssss.fff->" + dt1.ToString("HH:mm:ssss.fff"));             Console.WriteLine("f->" + dt1.ToString("f"));             Console.WriteLine("ff->" + dt1.ToString("ff"));             Console.WriteLine("fff->" + dt1.ToString("fff"));             Console.WriteLine("ffff->" + dt1.ToString("ffff"));             Console.WriteLine("fffff->" + dt1.ToString("fffff"));             Console.WriteLine("ffffff->" + dt1.ToString("ffffff"));             Console.WriteLine("HH:mm:ss.f->" + dt1.ToString("HH:mm:ss.f"));             Console.WriteLine("HH:mm:ss.ff->" + dt1.ToString("HH:mm:ss.ff"));             Console.WriteLine("HH:mm:ss.fff->" + dt1.ToString("HH:mm:ss.fff"));             Console.WriteLine("HH:mm:ss.ffff->" + dt1.ToString("HH:mm:ss.ffff"));             Console.WriteLine("HH:mm:ss.fffff->" + dt1.ToString("HH:mm:ss.fffff"));             Console.WriteLine("HH:mm:ss.ffffff->" + dt1.ToString("HH:mm:ss.ffffff"));             Console.WriteLine("t->" + dt1.ToString("t"));             Console.WriteLine("tt->" + dt1.ToString("tt"));             Console.WriteLine("ttt->" + dt1.ToString("ttt"));             Console.WriteLine("tttt->" + dt1.ToString("tttt"));             Console.WriteLine("t HH:mm:ss->" + dt1.ToString("t HH:mm:ss"));             Console.WriteLine("tt HH:mm:ss->" + dt1.ToString("tt HH:mm:ss"));             Console.WriteLine("ttt HH:mm:ss->" + dt1.ToString("ttt HH:mm:ss"));             Console.WriteLine("tttt HH:mm:ss->" + dt1.ToString("tttt HH:mm:ss"));             Console.ReadLine();