How to control json formatting with System.Web.OData (asp.net)

Question

here's my situation:

I'm working on an asp.net web api project with OData. I'm using Microsoft.Aspnet.OData NuGet package.

My intention is to intercept the serialization to json when a response is built.

Using System.Web.OData, I'm trying to extend System.Web.OData.Formatter.Serialization.DefaultODataSerializerProvider:

public class MyODataSerializerProvider : DefaultODataSerializerProvider
{

    public MyODataSerializerProvider(IServiceProvider rootContainer) : base(rootContainer)
    {

    }
}

Then, in my WebApiConfig.Register method I'd like to do the following:

config.Formatters.InsertRange(0, ODataMediaTypeFormatters.Create(new MyODataSerializerProvider(???), new DefaultODataDeserializerProvider(???)));

Where I put ??? above is the problem: with the last update of the System.Web.OData (version 6.0.0.0) they added support for Dependency Injection, but I don't know what to pass as rootContainer parameter.

I've read this: http://odata.github.io/odata.net/v7/#01-05-di-support but I don't need to create my Container Builder (at least I think so), I just wanna use the IServiceProvider that I think OData prepares. Am I right? Can i retrieve this IServiceProvider and pass it to my constructor?

A a more general question, is what I'm trying to do the right way to achieve my needs, that is to be able to control the serialization of the response?

Example of a situation: let's say that the response is a collection of entity type "Customer", with one of its properties named "Prop" of type int. When this collection is built for some specific user, I want to mask the real value of "Prop" and write "Prop" : 0 instead.

We tryed other roads to achieve this by code, but I think for our needs the best solution is to be able to control the json serialization.

Thanks.

Answer 1

Update (2022-05-19) in response to @piotreks comment:

Using Microsoft.AspNetCore.OData, Version=8.0.9.0:

using Microsoft.AspNetCore.OData.Formatter;
using Microsoft.AspNetCore.OData.Formatter.Serialization;
using Microsoft.OData;
using Microsoft.OData.Edm;
using System;

class MyODataSerializerProvider : ODataSerializerProvider
{
    public MyODataSerializerProvider(IServiceProvider serviceProvider)
        : base(serviceProvider)
    {
    }

    public override IODataEdmTypeSerializer GetEdmTypeSerializer(IEdmTypeReference edmType)
    {
        if (edmType.Definition.TypeKind == EdmTypeKind.Entity)
            return new MyODataResourceSerializer(this);
        else
            return base.GetEdmTypeSerializer(edmType);
    }
}

class MyODataResourceSerializer : ODataResourceSerializer
{
    public MyODataResourceSerializer(ODataSerializerProvider serializerProvider)
        : base(serializerProvider)
    {
    }

    public override ODataProperty CreateStructuralProperty(IEdmStructuralProperty structuralProperty, ResourceContext resourceContext)
    {
        ODataProperty
            property = base.CreateStructuralProperty(structuralProperty, resourceContext);

        if (resourceContext.StructuredType.FullTypeName() == typeof(Customer).FullName)
        {
            switch (property.Name)
            {
                case "Prop":
                    property.Value = 0;
                    break;
            }
        }

        return property;
    }
}

Registration:

public virtual void ConfigureServices(IServiceCollection services)
{
    IEdmModel
        model = BuildEdmModelForOData();

    services
        .AddControllers()
        .AddOData(oDataOptions =>
        {
            oDataOptions
                .AddRouteComponents("odata", model, serviceCollection =>
                {
                    serviceCollection
                        .AddSingleton<IODataSerializerProvider>(serviceProvider => new MyODataSerializerProvider(serviceProvider));
                });
        });
}

public IEdmModel BuildEdmModelForOData()
{
    ODataConventionModelBuilder
        builder = new();

    // Build model here

    return builder.GetEdmModel();
}

Original Answer:

I came across the same problem today. You register MyODataSerializerProvider as per this example:

    public void Register(HttpConfiguration config)
    {
        config.MapODataServiceRoute
        (
            "odata",
            "odata",
            BuildRoute
        );
    }

    private void BuildRoute(IContainerBuilder builder)
    {
        builder
            .AddService(ServiceLifetime.Singleton, s => BuildEdmModelForOData())
            .AddService<ODataSerializerProvider>(ServiceLifetime.Singleton, s => new MyODataSerializerProvider(s));
    }

    public IEdmModel BuildEdmModelForOData()
    {
        ODataConventionModelBuilder
            builder = new ODataConventionModelBuilder();

        // Build model here

        return builder.GetEdmModel();
    }

In relation to your more general question, it is possible to intercept and replace object values like this:

class MyODataSerializerProvider : DefaultODataSerializerProvider
{
    public MyODataSerializerProvider(IServiceProvider rootContainer)
        : base(rootContainer)
    {
    }

    public override ODataEdmTypeSerializer GetEdmTypeSerializer(IEdmTypeReference edmType)
    {
        if (edmType.Definition.TypeKind == EdmTypeKind.Entity)
            return new MyODataResourceSerializer(this);
        else
            return base.GetEdmTypeSerializer(edmType);
    }
}

class MyODataResourceSerializer : ODataResourceSerializer
{
    public MyODataResourceSerializer(ODataSerializerProvider serializerProvider)
        : base(serializerProvider)
    {
    }

    public override ODataProperty CreateStructuralProperty(IEdmStructuralProperty structuralProperty, ResourceContext resourceContext)
    {
        ODataProperty
            property = base.CreateStructuralProperty(structuralProperty, resourceContext);

        if (resourceContext.StructuredType.FullTypeName() == typeof(Customer).FullName)
        {
            switch (property.Name)
            {
                case "Prop":
                    property.Value = 0;
                    break;
            }
        }

        return property;
    }
}

It's also worth mentioning that returning null from CreateStructuralProperty suppresses the property entirely.

Hope this is still of assistance.