ASP.NET - Cómo pasar dd-MM-yyyyTHH:mm:ss a yyyy-MM-ddTHH:mm:ss

string FechaXML = "2016-10-03 02:55:03";

DateTime fechaResultadoXML = Convert.ToDateTime(FechaXML);

string fechaActual = DateTime.UtcNow.ToString("s"); // retorna  "2017-07-07T00:39:03"

DateTime fechaResultadoActual = Convert.ToDateTime(fechaActual);

fechaResultadoXML = 03-10-2016 02:55:03

fechaResultadoActual = 07-07-2017 00:39:03

fechaResultadoXML =  2016-10-03T02:55:03

fechaResultadoActual = 2017-07-07T00:39:03

Dim now As DateTime = DateTime.Now

Console.WriteLine(now.ToString("d"))

Console.WriteLine(now.ToString("D"))

Console.WriteLine(now.ToString("f"))

Console.WriteLine(now.ToString("F"))

Console.WriteLine(now.ToString("g"))

Console.WriteLine(now.ToString("G"))

Console.WriteLine(now.ToString("m"))

Console.WriteLine(now.ToString("M"))

Console.WriteLine(now.ToString("o"))

Console.WriteLine(now.ToString("O"))

Console.WriteLine(now.ToString("s"))

Console.WriteLine(now.ToString("t"))

Console.WriteLine(now.ToString("T"))

Console.WriteLine(now.ToString("u"))

Console.WriteLine(now.ToString("U"))

Console.WriteLine(now.ToString("y"))

Console.WriteLine(now.ToString("Y"))

Console.WriteLine(now.ToString("s"))

DateTime dt = DateTime.Now;

Console.WriteLine(string.Format("Fecha: {0:yyyy-MM-dd HH:mm:ss}", dt));