StartupOData.cs

public class Startup
{
  ...

  public void Configure(IApplicationBuilder app, IHostingEnvironment env)
  {
      ...
      app.UseMvc(routerBuilder =>
      {
          // 2. Enable Dependency Injection on current routes
          routerBuilder.EnableDependencyInjection(builder =>
                    {
                        builder
                        .AddService(Microsoft.OData.ServiceLifetime.Singleton, typeof(ODataUriResolver), sp => new StringAsEnumResolver())
                        .AddService(Microsoft.OData.ServiceLifetime.Singleton, typeof(ODataUriResolver), sp => new UnqualifiedCallAndEnumPrefixFreeResolver { EnableCaseInsensitive = true });
                    });
          ...
      });
  }
}