Question

I’m trying to return from MVC 4 web api ApiController objects generated from entity framework 4 edmx, with accept:json/application.

The problem is json formatter returns also the Navigation Properties, which I don’t want to return (I want to return only the Primitive Properties).

So I’ve looked in the entity framework 4 code generated, in the Navigation Properties, and there are only XmlIgnoreAttribute and SoapIgnoreAttribute while I need JsonIgnoreAttribute.

I cannot change the code generated because it will be overwritten in the next change to the edmx,
so how can I configure that the model generation will be produced with JsonIgnoreAttribute?

Thank you

Answer 1

Ok, I found out what to do.
We need to use custom DefaultContractResolver in this way:

public class ExcludeEntityKeyContractResolver : DefaultContractResolver
{
    private static Type mCollectionType = typeof(System.Data.Objects.DataClasses.RelatedEnd);

    protected override IList<JsonProperty> CreateProperties(Type type, MemberSerialization memberSerialization)
    {
        var members = GetSerializableMembers(type);

        IList<JsonProperty> properties = base.CreateProperties(type, memberSerialization);
        IList<JsonProperty> serializeProperties = new List<JsonProperty>();

        for (int i = 0; i < properties.Count; i++)
        {
            var memberInfo = members.Find(p => p.Name == properties[i].PropertyName);
            if (!memberInfo.GetCustomAttributes(false).Any(a => a is SoapIgnoreAttribute) && properties[i].PropertyType != typeof(System.Data.EntityKey))
            {
                serializeProperties.Add(properties[i]);
            }
        }
        return serializeProperties;
    }
}

and in Global.asax:

        JsonSerializerSettings serializerSettings = new JsonSerializerSettings();
        serializerSettings.ContractResolver = new ExcludeEntityKeyContractResolver();
        var jsonMediaTypeFormatter = new JsonMediaTypeFormatter();
        jsonMediaTypeFormatter.SerializerSettings = serializerSettings;
        GlobalConfiguration.Configuration.Formatters.Insert(0, jsonMediaTypeFormatter);

and don’t worry about performance, as CreateProperties will only be called once for every type for the whole application duration 🙂