protobuf-net: bcl.DateTime to xs:dateTime?

I would like bcl.DateTime elements to be converted to xs:dateTime in XPathDocument

This might be related to issue #69

I created a small test project like this

test.proto

import "bcl.proto";

message Test {
    required bcl.DateTime tAsOf = 1;    
}

program.cs

using System;
using System.IO;
using System.Xml;
using System.Xml.Serialization;
using System.Xml.XPath;
using ProtoBuf;
using test;

namespace DateTimeXML
{
    class Program
    {
        static void Main()
        {
            var d = new bcl.DateTime() {value = new DateTime(2011, 7, 31).Ticks};
            var t = new Test() {tAsOf = d};
            var xml = Serialize(t);
            WriteXpathDocument(xml, "c:\\temp\\xpathdoc.xml");
        }

        private static XPathDocument Serialize(Test obj)
        {
            XPathDocument xmlDoc;
            Serializer.PrepareSerializer<Test>();

            var x = new XmlSerializer(obj.GetType());
            using (var memoryStream = new MemoryStream())
    开发者_如何学JAVA        {
                using (TextWriter w = new StreamWriter(memoryStream))
                {
                    x.Serialize(w, obj);
                    memoryStream.Position = 0;
                    xmlDoc = new XPathDocument(memoryStream);
                }
            }
            return xmlDoc;
        }

        private static void WriteXpathDocument(XPathDocument xpathDoc, string filename)
        {
            // Create XpathNaviagtor instances from XpathDoc instance.
            var objXPathNav = xpathDoc.CreateNavigator();

            // Create XmlWriter settings instance.
            var objXmlWriterSettings = new XmlWriterSettings();
            objXmlWriterSettings.Indent = true;

            // Create disposable XmlWriter and write XML to file.
            using (var objXmlWriter = XmlWriter.Create(filename, objXmlWriterSettings))
            {
                objXPathNav.WriteSubtree(objXmlWriter);
                objXmlWriter.Close();
            }
        }
    }     
}

it creates the following xml file:

<?xml version="1.0" encoding="utf-8"?>
<Test xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <tAsOf>
    <value>634476672000000000</value>
  </tAsOf>
</Test>

Interesting; the bcl.DateTime type is really intended to represent the internal DateTime format, and is not really intended for use directly. I should probably correct that to interpret bcl.DateTime as DateTime during translation, but the more typical usage here (since you are talking about .NET types, such as DateTime) would be code-first, i.e.

[ProtoContract]
class Test {
    [ProtoMember(1, IsRequired = true)]
    public DateTime AsOf {get;set;}  
}

this should then work as desired for both protobuf and xs purposes.

Do you need .proto here? I can patch that, I just want to know if it is required.

Re the comment / update, and re using .proto - I would strongly suggest using the most basic common format for the time value - possibly a long (or a string maybe), and either use shim properties in a partial class to expose a twin DateTime value to xs, or (perhaps better) use a separate DTO to represent the protobuf / xs aspects and map between them. A .proto isn't going to love bcl.DateTime between platforms.