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jennings/Program.cs

Last active Dec 5, 2015
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A sample program for Stack Overflow question 34111695 (http://stackoverflow.com/q/34111695/19818)
// See: http://stackoverflow.com/q/34111695/19818
namespace StackOverflow34111695
{
using System;
using System.IO;
using System.Xml;
using System.Xml.Schema;
using System.Xml.Serialization;
public struct Maybe<T> : IXmlSerializable where T : class
{
public readonly T _value;
public Maybe(T value)
{
_value = value;
}
public override string ToString()
{
if (_value == null)
{
return "None";
}
return string.Format("Some({0})", _value);
}
XmlSchema IXmlSerializable.GetSchema() { return null; }
void IXmlSerializable.ReadXml(XmlReader reader)
{
var value = (T)reader.ReadElementContentAs(typeof(T), null);
var maybe = new Maybe<T>(value);
this = maybe;
}
void IXmlSerializable.WriteXml(XmlWriter writer)
{
if (_value == null)
{
// I want to emit nothing
}
else
{
writer.WriteValue(_value);
}
}
}
[XmlRoot("SomeObject")]
public class SomeObjectV1
{
public string MaybeAString { get; set; }
}
[XmlRoot("SomeObject")]
public class SomeObjectV2
{
public Maybe<string> MaybeAString { get; set; }
}
class Program
{
static void Main(string[] args)
{
var obj = new SomeObjectV2 { MaybeAString = new Maybe<string>(null) };
Console.WriteLine("ORIGINAL PROPERTY VALUE: <{0}>", obj.MaybeAString);
Console.WriteLine();
// V2 of the app serializes a value
var serializerV2 = new XmlSerializer(typeof(SomeObjectV2));
var writer = new StringWriter();
serializerV2.Serialize(writer, obj);
var serialized = writer.ToString();
Console.WriteLine("SERIALIZED VALUE:");
Console.WriteLine(serialized);
Console.WriteLine();
// V1 of the app deserializes the value
var serializerV1 = new XmlSerializer(typeof(SomeObjectV1));
var reader = new StringReader(serialized);
var deserialized = (SomeObjectV1)serializerV1.Deserialize(reader);
Console.WriteLine("DESERIALIZED PROPERTY: <{0}>", deserialized.MaybeAString);
Console.WriteLine(deserialized.MaybeAString == null ? "Yay! It worked!" : "It's an empty string, not null :(");
Console.WriteLine();
Console.WriteLine("Press any key to exit.");
Console.ReadKey();
}
}
}
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