Btukfyl

In Microsoft.AspNet.OData V5.9.1 and lower, you could enable alternate keys by calling EnableAlternateKeys() in the WebApiConfig.cs like so:

config.EnableAlternateKeys(true);

This option has been removed along with others like :

config.EnableCaseInsensitive(true);

How do you turn the EnableAlternateKeys option on in Microsoft.AspNet.OData V6+?

This has changed in OData WebAPI 6. Since v6 Dependency Injection has been introduced (see docs). This means the old way of configuring your service has been changed. From now on you should register all necessary services and routes in the MapODataServiceRoute method

public static void Register(HttpConfiguration config)

{

    // Web API configuration and services

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



    setErrorDetailPolicy();

    var model = BuildEdmModel();



    // Web API routes

    config.MapODataServiceRoute("routeName", "routePrefix", builder =>

        builder.AddDefaultODataServices()

        .AddService<IEdmModel>(ServiceLifetime.Singleton, s => model)

        .AddService<IEnumerable<IODataRoutingConvention>>(ServiceLifetime.Singleton, sp => ODataRoutingConventions.CreateDefaultWithAttributeRouting("routeContact", config))

        .AddService<ODataUriResolver>(ServiceLifetime.Singleton, s => new AlternateKeysODataUriResolver(model))

    );

}

The important line here is the last one:

.AddService<ODataUriResolver>(ServiceLifetime.Singleton, s => new AlternateKeysODataUriResolver(model))

After this is enabled I found that my model had issues recognizing the AddAlternateKeyAnnotation extension method. This was solved by casting the instance to an EdmModel (instead of using the IEdmModel it was). My ModelBuilder class looks something like this:

    internal static IEdmModel GetModel()

    {

        ODataConventionModelBuilder builder = new ODataConventionModelBuilder();

        builder.Namespace = "MyNamespace";



        var personsSet = builder.EntitySet<PersonDTO>("Persons");

        builder.EntityType<PersonDTO>().HasKey(k => k.Id);



        var model = builder.GetEdmModel();



        // model is built, add alternateKey annotation as necessary

        // first, find entity type

        IEdmEntityType t = model.FindDeclaredEntitySet("Persons").EntityType();



        // now find the properties we want to use as alternateKey

        var firstNameProp = t.FindProperty("FirstName");

        var lastNameProp = t.FindProperty("LastName");



        // and finally add the annotation

        ((EdmModel)model).AddAlternateKeyAnnotation(t, new Dictionary<string, IEdmProperty> {

            {

                "FirstName", firstNameProp

            },

            {

                "LastName", lastNameProp

            }

        });



        return model;

    }

Note that there are still a couple of convenience methods. From the documentation:

You might also find that we still preserve the previous overloads of
MapODataServiceRoute which take batch handlers, path handlers, HTTP
message handlers, etc. They are basically wrapping the first overload
that takes a configureAction. The reason why we keep them is that we
want to give the users convenience to create OData services and
bearings to the APIs they are familiar with.

If you're wondering what the first line does:

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

This is because in OData v6 by default all query options are disabled (again, see docs). You should either enable them on each controller/action, or do as I did, and enable them globally (which is what the above line does).

Something missing from jonathan.meesschaert answer is the signature for your action in the OData controller.

In my case I had the following alernate key:

((EdmModel)edmModel).AddAlternateKeyAnnotation(

entityType,

new Dictionary<string, IEdmProperty>() {

    { "Text", edmProperty }

});

and the asociated controller action was:

public MenuItem Get([FromODataUri]string keyText)

Note that you don't need to use [HttpGet] or [ODataRoute("Menus(Text={Text})")] to get it working. However, the crucial part is that I had to append key to the parameter name. Without that it didn't work on OData v7.1.0