如何将DateTime .NET数据类型转换为W3C XML DateTime数据类型字符串并返回？

// DateTime to W3C dateTime string
string formatString= \"yyyy-MM-ddTHH:mm:ss.fffffffzzz\";
dateTimeField.ToString(formatString) ;

// W3C dateTime string to DateTime 
System.Globalization.CultureInfo cInfo= new System.Globalization.CultureInfo(\"en-US\", true);
dateTimeField= System.DateTime.ParseExact(stringValue, formatString, cInfo);

var w3cStringFormat = XmlConvert.ToString(DateTime.Now);

var dateTime = XmlConvert.ToDateTime(w3cStringFormat);

var now = DateTime.Now;
Console.WriteLine(now.ToUniversalTime().ToString());
var nowString = now.ToUniversalTime().ToString(\"yyyy-MM-ddTHH:mm:ssZ\");
Console.WriteLine(nowString);

var nowAgain = DateTime.ParseExact(nowString, \"yyyy-MM-ddTHH:mm:ssZ\", null);
Console.WriteLine(nowAgain.ToUniversalTime().ToString());

Console.ReadLine();

public class LogEntry
{
  public string Details { get; set; }
  public DateTime LogDate { get; set; }
}

[Test]
public void WriteJsonDates()
{
  LogEntry entry = new LogEntry
  {
    LogDate = new DateTime(2009, 2, 15, 0, 0, 0, DateTimeKind.Utc),
    Details = \"Application started.\"
  };

  string defaultJson = JsonConvert.SerializeObject(entry);
  // {\"Details\":\"Application started.\",\"LogDate\":\"\\/Date(1234656000000)\\/\"}

  string javascriptJson = JsonConvert.SerializeObject(entry, new JavaScriptDateTimeConverter());
  // {\"Details\":\"Application started.\",\"LogDate\":new Date(1234656000000)}

  string isoJson = JsonConvert.SerializeObject(entry, new IsoDateTimeConverter());
  // {\"Details\":\"Application started.\",\"LogDate\":\"2009-02-15T00:00:00Z\"}
}

DateTime someDateTime = DateTime.Now.AddDays(5);
System.Xml.Serialization.XmlSerializer ser = new System.Xml.Serialization.XmlSerializer(typeof(DateTime));
System.IO.MemoryStream ms = new System.IO.MemoryStream();
// converting to w3c xml
ser.Serialize(ms, someDateTime);

//**Edited**
ms.Position = 0;
//**Edited**

System.IO.StreamReader sr = new System.IO.StreamReader(ms);
string w3cxml = sr.ReadToEnd();

sr.Close();
ms.Close();

// doing reverse
System.IO.StringReader reader = new System.IO.StringReader(w3cxml);

DateTime thatDateTime = (DateTime)ser.Deserialize(reader);

reader.Close();