Change casing of JSON properties between api versions using Microsoft's ASP.NET API Versioning for Web API 2 and ODATA?

Question

I am introducing API versioning to an existing API. The existing JSON uses Pascal casing for its property names e.g. "FooBar": "foo". For v2 of the API, I would like to use the common camel casing, "fooBar": "foo". I need to keep v1 Pascal casing so that it does not impact any client that is already pulling that version of the API.

My project is

• ASP.NET MVC 5.2.7
• ASP.NET WEB API 5.2.7
• ASP.NET ODATA 7.4.0
• ASP.NET WEB API Versioning 4.0.0

My configuration is as follows

public static class WebApiConfig
{
    public static void Register(HttpConfiguration configuration)
    {
        configuration.AddApiVersioning(options => options.ReportApiVersions = true);

        var modelBuilder = new VersionedODataModelBuilder(configuration);

        AppDomain.CurrentDomain.GetAssemblies()
            .SelectMany(x => x.GetTypes())
            .Where(x => typeof(IModelConfiguration).IsAssignableFrom(x) && !x.IsInterface && !x.IsAbstract)
            .ForEach(t => modelBuilder.ModelConfigurations.Add((IModelConfiguration)Activator.CreateInstance(t)));

        var models = modelBuilder.GetEdmModels();

        configuration.MapVersionedODataRoutes("odata-bypath", "api/v{apiVersion}", models, builder =>
        {
            builder.AddService<IODataPathHandler>(Singleton, sp => new DefaultODataPathHandler { UrlKeyDelimiter = Parentheses });
            builder.AddService<ODataUriResolver>(Singleton, sp => new UnqualifiedCallAndEnumPrefixFreeResolver { EnableCaseInsensitive = true });
        });

        configuration.Count().Filter().OrderBy().Expand().Select().MaxTop(null);

        configuration.MapHttpAttributeRoutes();
    }
}

After reading through the docs and specifically Versioned ODataModelBuilder I have not found a way to change the casing based on which version of the API the model is being built for. I can get it to be all Pascal casing or all camel casing, but not v1 Pascal casing and v2 camel casing.

Adjusting the above configuration

var modelBuilder = new VersionedODataModelBuilder( configuration )
{
    ModelBuilderFactory = () => new ODataConventionModelBuilder().EnableLowerCamelCase()
};

would use camel casing (yes I know the explicit call is unnecessary since it is the default). Then I built my own extension method ODataConventialModelBuilder().EnablePascalCase() that mimicked EnableLowerCamelCase() method to get Pascal casing to work.

var modelBuilder = new VersionedODataModelBuilder( configuration )
{
    ModelBuilderFactory = () => new ODataConventionModelBuilder().EnablePascalCase()
};

However, I could never find a way to know which version of the API I was building the model for.

At one point, I thought I had it using OnModelCreating to add

((ODataConventionModelBuilder) builder).OnModelCreating += new PascalCaser().ApplyCase;

to each of the v1 IModelConfiguration classes, but it didn't work once I was building multiple models.

Is there a way to change the JSON property naming based on which API version the model is for?

Answer 1

Using the OData Model Configurations approach described here first add a class that derives from IModelConfiguration to your project.

Something like this:

public class VersionedModelConfiguration : IModelConfiguration
{
    private void ConfigureV1(ODataModelBuilder builder)
    {
        builder.EntitySet<Product>("Products");
    }

    private void ConfigureV2(ODataModelBuilder builder)
    {
        if (builder.GetType().Equals(typeof(ODataConventionModelBuilder)))
        {
            ((ODataConventionModelBuilder)builder).EnableLowerCamelCase();
        }
        builder.EntitySet<Product>("Products");
    }

    public void Apply(ODataModelBuilder builder, ApiVersion apiVersion)
    {

        switch (apiVersion.MajorVersion)
        {
            case 1:
                ConfigureV1(builder);
                break;
            case 2:
                ConfigureV2(builder);
                break;
            default:
                ConfigureV1(builder);
                break;
        }
    }
}

Then in Register method:

// ...
var modelBuilder = new VersionedODataModelBuilder(configuration)
{
    ModelBuilderFactory = () => new ODataConventionModelBuilder(),
    ModelConfigurations = { new VersionedModelConfiguration() }
};

var models = modelBuilder.GetEdmModels();
// ...

Don't be tempted to leave out the line ModelBuilderFactory = () => new ODataConventionModelBuilder()

/api/v1/$metadata:

<?xml version="1.0" encoding="UTF-8"?>
<edmx:Edmx xmlns:edmx="http://docs.oasis-open.org/odata/ns/edmx" Version="4.0">
   <edmx:DataServices>
      <Schema xmlns="http://docs.oasis-open.org/odata/ns/edm" Namespace="NS.Models">
         <EntityType Name="Product">
            <Key>
               <PropertyRef Name="Id" />
            </Key>
            <Property Name="Id" Type="Edm.Int32" Nullable="false" />
            <Property Name="Name" Type="Edm.String" />
         </EntityType>
      </Schema>
      <Schema xmlns="http://docs.oasis-open.org/odata/ns/edm" Namespace="Default">
         <EntityContainer Name="Container">
            <EntitySet Name="Products" EntityType="NS.Models.Product" />
         </EntityContainer>
      </Schema>
   </edmx:DataServices>
</edmx:Edmx>

/api/v2/$metadata:

<?xml version="1.0" encoding="UTF-8"?>
<edmx:Edmx xmlns:edmx="http://docs.oasis-open.org/odata/ns/edmx" Version="4.0">
   <edmx:DataServices>
      <Schema xmlns="http://docs.oasis-open.org/odata/ns/edm" Namespace="NS.Models">
         <EntityType Name="Product">
            <Key>
               <PropertyRef Name="id" />
            </Key>
            <Property Name="id" Type="Edm.Int32" Nullable="false" />
            <Property Name="name" Type="Edm.String" />
         </EntityType>
      </Schema>
      <Schema xmlns="http://docs.oasis-open.org/odata/ns/edm" Namespace="Default">
         <EntityContainer Name="Container">
            <EntitySet Name="Products" EntityType="NS.Models.Product" />
         </EntityContainer>
      </Schema>
   </edmx:DataServices>
</edmx:Edmx>