c# - XSD.EXE + JSON.NET - How to deal with xxxSpecified generated members?

Question

When using XSD.EXE to generate classes from an XML Schema, it generates xxxSpecified members of any primitives of a given object:

<xs:complexType name ="Foo">
    <xs:all>
      <xs:element name ="Count" type = "xs:integer"/>
    </xs:all>
</xs:complexType>

....generates:

public class Foo
{
    public int Count { get; set; }
    public bool CountSpecified { get; set; }
}

It appears the latest version of JSON.NET can automatically set these properties when deserializing.

string request = "{ Count : 10 }";
var object = JsonConvert.Deserialize<Foo>(request)
Assert.IsTrue(object.Count = 10); // Yup
Assert.IsTrue(object.CountSpecified == true);  //Also yup - JSON.NET works!

However, when going the other way, the xxxSpecified properties are included in the JSON output, which is incorrect, as it is not part of the schema.

string request = JsonConvert.Serialize(object); 
//{  
//   Count: 10, 
//   CountSpecified : true    <-- This is incorrect - should not be output 
//}

Is there any setting I am missing that controls whether to output the xxxSpecified attributes? How can I suppress it?

(Note: This is a permutation of a question answered here:

JSON.NET, XmlSerializer and "Specified" property

...but it involves creating extension classes, which is not possible for me, as there are hundreds of classes in the schema and I can't change the inheritance hierarchy. So the answer won't work. Looking for another way.)

Answer 1

You can create your own contract resolver to filter out xxxSpecified properties:

public class SkipSpecifiedContractResolver : DefaultContractResolver
{
    // As of 7.0.1, Json.NET suggests using a static instance for "stateless" contract resolvers, for performance reasons.
    // http://www.newtonsoft.com/json/help/html/ContractResolver.htm
    // http://www.newtonsoft.com/json/help/html/M_Newtonsoft_Json_Serialization_DefaultContractResolver__ctor_1.htm
    // "Use the parameterless constructor and cache instances of the contract resolver within your application for optimal performance."
    static SkipSpecifiedContractResolver instance;

    static SkipSpecifiedContractResolver() { instance = new SkipSpecifiedContractResolver(); }

    public static SkipSpecifiedContractResolver Instance { get { return instance; } }

    protected override IList<JsonProperty> CreateProperties(Type type, MemberSerialization memberSerialization)
    {
        var properties = base.CreateProperties(type, memberSerialization);
        ILookup<string, JsonProperty> lookup = null;
        foreach (var property in properties)
        {
            if (property.GetIsSpecified != null && property.SetIsSpecified != null)
            {
                var name = property.UnderlyingName + "Specified";
                lookup = lookup ?? properties.ToLookup(p => p.UnderlyingName);
                var specified = lookup[name]
                    // Possibly also check for [XmlIgnore] being applied.  While not shown in the question, xsd.exe will always
                    // apply [XmlIgnore] to xxxSpecified tracking properties.
                    //.Where(p => p.AttributeProvider.GetAttributes(typeof(System.Xml.Serialization.XmlIgnoreAttribute),true).Any())
                    .SingleOrDefault();
                if (specified != null)
                    specified.Ignored = true;
            }
        }
        return properties;
    }
}

Then use it like:

var settings = new JsonSerializerSettings { ContractResolver = SkipSpecifiedContractResolver.Instance };
var object = JsonConvert.DeserializeObject<Foo>(request, settings);

If you want to do this always, you can set the contract resolver in the global JsonConvert.DefaultSettings:

JsonConvert.DefaultSettings = (() =>
{
    return new JsonSerializerSettings { ContractResolver = SkipSpecifiedContractResolver.Instance };
});