ASP.NET Web API OData error: ValueFactory attempted to access the Value property of this instance.

After following the tutorial here; https://docs.microsoft.com/en-us/aspnet/web-api/overview/odata-support-in-aspnet-web-api/odata-v4/create-an-odata-v4-endpoint I got the following error when I tried to run the OData endpoint:

System.InvalidOperationException was caught

  HResult=-2146233079

  Message=ValueFactory attempted to access the Value property of this instance.

  Source=mscorlib

  StackTrace:

       at System.Lazy`1.CreateValue()

       at System.Lazy`1.LazyInitValue()

       at System.Lazy`1.get_Value()

       at System.Web.Http.Dispatcher.DefaultHttpControllerSelector.GetControllerMapping()

       at System.Web.Http.Routing.AttributeRoutingMapper.AddRouteEntries(SubRouteCollection collector, HttpConfiguration configuration, IInlineConstraintResolver constraintResolver, IDirectRouteProvider directRouteProvider)

       at System.Web.Http.Routing.AttributeRoutingMapper.<>c__DisplayClass2.<>c__DisplayClass4.<MapAttributeRoutes>b__1()

       at System.Web.Http.Routing.RouteCollectionRoute.EnsureInitialized(Func`1 initializer)

       at System.Web.Http.Routing.AttributeRoutingMapper.<>c__DisplayClass2.<MapAttributeRoutes>b__0(HttpConfiguration config)

       at System.Web.Http.HttpConfiguration.ApplyControllerSettings(HttpControllerSettings settings, HttpConfiguration configuration)

       at System.Web.Http.Controllers.HttpControllerDescriptor.InvokeAttributesOnControllerType(HttpControllerDescriptor controllerDescriptor, Type type)

       at System.Web.Http.Controllers.HttpControllerDescriptor.InvokeAttributesOnControllerType(HttpControllerDescriptor controllerDescriptor, Type type)

       at System.Web.Http.Controllers.HttpControllerDescriptor.Initialize()

       at System.Web.Http.Controllers.HttpControllerDescriptor..ctor(HttpConfiguration configuration, String controllerName, Type controllerType)

       at System.Web.Http.Dispatcher.DefaultHttpControllerSelector.InitializeControllerInfoCache()

       at System.Lazy`1.CreateValue()

       at System.Lazy`1.LazyInitValue()

       at System.Lazy`1.get_Value()

       at System.Web.Http.Dispatcher.DefaultHttpControllerSelector.GetControllerMapping()

       at System.Web.OData.Routing.Conventions.AttributeRoutingConvention.<>c__DisplayClass1.<.ctor>b__0(HttpConfiguration config)

       at System.Web.Http.Routing.AttributeRoutingMapper.<>c__DisplayClass2.<MapAttributeRoutes>b__0(HttpConfiguration config)

       at System.Web.Http.HttpConfiguration.EnsureInitialized()

       at System.Web.Http.GlobalConfiguration.Configure(Action`1 configurationCallback)

This was an error message I’ve never seen before, so I had no immediate clue about what’s going on. Here is how our API configuration looks like:

	public static class WebApiConfig
	{
	public static void Register(HttpConfiguration config)
	{
	// OData config
	ODataModelBuilder builder = new ODataConventionModelBuilder();
	builder.EntitySet<Product>("Products");
	config.MapODataServiceRoute(
	routeName: "ODataRoute",
	routePrefix: null,
	model: builder.GetEdmModel());
	// Web API routes
	config.MapHttpAttributeRoutes();
	config.Routes.MapHttpRoute(
	name: "DefaultApi",
	routeTemplate: "api/{controller}/{id}",
	defaults: new { id = RouteParameter.Optional }
	);
	}
	}

view raw WebApiConfig.cs hosted with ❤ by GitHub

We found out that by changing the order in which we register the routes solved the problem:

	public static class WebApiConfig
	{
	public static void Register(HttpConfiguration config)
	{
	// Web API routes, should be set first otherwise we'll get an error
	config.MapHttpAttributeRoutes();
	// OData config
	ODataModelBuilder builder = new ODataConventionModelBuilder();
	builder.EntitySet<Product>("Products");
	config.MapODataServiceRoute(
	routeName: "ODataRoute",
	routePrefix: null,
	model: builder.GetEdmModel());
	config.Routes.MapHttpRoute(
	name: "DefaultApi",
	routeTemplate: "api/{controller}/{id}",
	defaults: new { id = RouteParameter.Optional }
	);
	}
	}

view raw WebApiConfigFixed.cs hosted with ❤ by GitHub