WebAPI and ODataController return 406 Not Acceptable

Question

Before adding OData to my project, my routes where set up like this:

       config.Routes.MapHttpRoute(
            name: \"ApiById\",
            routeTempl         


        

Answer 1

My error and fix was different from the answers above.

The specific issue I had was accessing a mediaReadLink endpoint in my ODataController in WebApi 2.2.

OData has a 'default stream' property in the spec which allows a returned entity to have an attachment. So the e.g. json object for filter etc describes the object, and then there is a media link embedded which can also be accessed. In my case it is a PDF version of the object being described.

There's a few curly issues here, the first comes from the config:

<system.web>
  <customErrors mode="Off" />
  <compilation debug="true" targetFramework="4.7.1" />
  <httpRuntime targetFramework="4.5" />
  <!-- etc -->
</system.web>

At first I was trying to return a FileStreamResult, but i believe this isn't the default net45 runtime. so the pipeline can't format it as a response, and a 406 not acceptable ensues.

The fix here was to return a HttpResponseMessage and build the content manually:

    [System.Web.Http.HttpGet]
    [System.Web.Http.Route("myobjdownload")]
    public HttpResponseMessage DownloadMyObj(string id)
    {
        try
        {
            var myObj = GetMyObj(id); // however you do this                
            if (null != myObj )
            {
                HttpResponseMessage result = Request.CreateResponse(HttpStatusCode.OK);

                byte[] bytes = GetMyObjBytes(id); // however you do this
                result.Content = new StreamContent(bytes); 

                result.Content.Headers.ContentType = new MediaTypeWithQualityHeaderValue("application/pdf");
                result.Content.Headers.LastModified = DateTimeOffset.Now;  
                result.Content.Headers.ContentDisposition = new ContentDispositionHeaderValue(DispositionTypeNames.Attachment)
                {
                    FileName = string.Format("{0}.pdf", id),
                    Size = bytes.length,
                    CreationDate = DateTimeOffset.Now,
                    ModificationDate = DateTimeOffset.Now
                };

                 return  result;
            }
        }
        catch (Exception e)
        {
            // log, throw 
        }
        return null;
    }

My last issue here was getting an unexpected 500 error after returning a valid result. After adding a general exception filter I found the error was Queries can not be applied to a response content of type 'System.Net.Http.StreamContent'. The response content must be an ObjectContent.. The fix here was to remove the [EnableQuery] attribute from the top of the controller declaration, and only apply it at the action level for the endpoints that were returning entity objects.

The [System.Web.Http.Route("myobjdownload")] attribute is how to embed and use media links in OData V4 using web api 2.2. I'll dump the full setup of this below for completeness.

Firstly, in my Startup.cs:

[assembly: OwinStartup(typeof(MyAPI.Startup))]
namespace MyAPI
{
    public class Startup
    {
        public void Configuration(IAppBuilder app)
        {
            // DI etc
            // ...
            GlobalConfiguration.Configure(ODataConfig.Register); // 1st
            GlobalConfiguration.Configure(WebApiConfig.Register); // 2nd      
            // ... filters, routes, bundles etc
            GlobalConfiguration.Configuration.EnsureInitialized();
        }
    }
}

ODataConfig.cs:

// your ns above
public static class ODataConfig
{
    public static void Register(HttpConfiguration config)
    {
        ODataConventionModelBuilder builder = new ODataConventionModelBuilder();
        var entity1 = builder.EntitySet<MyObj>("myobj");
        entity1.EntityType.HasKey(x => x.Id);
        // etc

        var model = builder.GetEdmModel();

        // tell odata that this entity object has a stream attached
        var entityType1 = model.FindDeclaredType(typeof(MyObj).FullName);
        model.SetHasDefaultStream(entityType1 as IEdmEntityType, hasStream: true);
        // etc

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

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

        // note: this calls config.MapHttpAttributeRoutes internally
        config.Routes.MapODataServiceRoute("ODataRoute", "data", model);

        // in my case, i want a json-only api - ymmv
        config.Formatters.JsonFormatter.SupportedMediaTypes.Add(new MediaTypeWithQualityHeaderValue("text/html"));
        config.Formatters.Remove(config.Formatters.XmlFormatter);

    }
}

WebApiConfig.cs:

// your ns above
public static class WebApiConfig
{
    public static void Register(HttpConfiguration config)
    {
        // https://stackoverflow.com/questions/41697934/catch-all-exception-in-asp-net-mvc-web-api
        //config.Filters.Add(new ExceptionFilter());

        // ymmv
        var cors = new EnableCorsAttribute("*", "*", "*");
        config.EnableCors(cors);

        // so web api controllers still work
        config.Routes.MapHttpRoute(
            name: "DefaultApi",
            routeTemplate: "{controller}/{id}",
            defaults: new { id = RouteParameter.Optional }
        );

        // this is the stream endpoint route for odata
        config.Routes.MapHttpRoute("myobjdownload", "data/myobj/{id}/content", new { controller = "MyObj", action = "DownloadMyObj" }, null);
        // etc MyObj2
    }
}

MySerializerProvider.cs:

public class MySerializerProvider: DefaultODataSerializerProvider
{
    private readonly Dictionary<string, ODataEdmTypeSerializer> _EntitySerializers;

    public SerializerProvider()
    {
        _EntitySerializers = new Dictionary<string, ODataEdmTypeSerializer>();
        _EntitySerializers[typeof(MyObj).FullName] = new MyObjEntitySerializer(this);
        //etc 
    }

    public override ODataEdmTypeSerializer GetEdmTypeSerializer(IEdmTypeReference edmType)
    {
        if (edmType.IsEntity())
        {
            string stripped_type = StripEdmTypeString(edmType.ToString());
            if (_EntitySerializers.ContainsKey(stripped_type))
            {
                return _EntitySerializers[stripped_type];
            }
        }            
        return base.GetEdmTypeSerializer(edmType);
    }

    private static string StripEdmTypeString(string t)
    {
        string result = t;
        try
        {
            result = t.Substring(t.IndexOf('[') + 1).Split(' ')[0];
        }
        catch (Exception e)
        {
            //
        }
        return result;
    }
}

MyObjEntitySerializer.cs:

public class MyObjEntitySerializer : DefaultStreamAwareEntityTypeSerializer<MyObj>
{
    public MyObjEntitySerializer(ODataSerializerProvider serializerProvider) : base(serializerProvider)
    {
    }

    public override Uri BuildLinkForStreamProperty(MyObj entity, EntityInstanceContext context)
    {
        var url = new UrlHelper(context.Request);
        string id = string.Format("?id={0}", entity.Id);
        var routeParams = new { id }; // add other params here
        return new Uri(url.Link("myobjdownload", routeParams), UriKind.Absolute);            
    }

    public override string ContentType
    {
        get { return "application/pdf"; }            
    }
}

DefaultStreamAwareEntityTypeSerializer.cs:

public abstract class DefaultStreamAwareEntityTypeSerializer<T> : ODataEntityTypeSerializer where T : class
{
    protected DefaultStreamAwareEntityTypeSerializer(ODataSerializerProvider serializerProvider)
        : base(serializerProvider)
    {
    }

    public override ODataEntry CreateEntry(SelectExpandNode selectExpandNode, EntityInstanceContext entityInstanceContext)
    {
        var entry = base.CreateEntry(selectExpandNode, entityInstanceContext);

        var instance = entityInstanceContext.EntityInstance as T;

        if (instance != null)
        {
            entry.MediaResource = new ODataStreamReferenceValue
            {
                ContentType = ContentType,
                ReadLink = BuildLinkForStreamProperty(instance, entityInstanceContext)
            };
        }
        return entry;
    }

    public virtual string ContentType
    {
        get { return "application/octet-stream"; }
    }

    public abstract Uri BuildLinkForStreamProperty(T entity, EntityInstanceContext entityInstanceContext);
}

The end result is my json objects get these odata properties embedded:

odata.mediaContentType=application/pdf
odata.mediaReadLink=http://myhost/data/myobj/%3fid%3dmyid/content

And the following the decoded media link http://myhost/data/myobj/?id=myid/content fires the endpoint on your MyObjController : ODataController.

Answer 2

The problem I had was that i had named my entityset "Products" and had a ProductController. Turns out the name of the entity set must match your controller name.

So

builder.EntitySet<Product>("Products");

with a controller named ProductController will give errors.

/api/Product will give a 406

/api/Products will give a 404

So using some of the new C# 6 features we can do this instead:

builder.EntitySet<Product>(nameof(ProductsController).Replace("Controller", string.Empty));

Answer 3

In my case I needed to change a non-public property setter to public.

public string PersonHairColorText { get; internal set; }

Needed to be changed to:

public string PersonHairColorText { get; set; }

Answer 4

For me the problem was, that I used LINQ and selected the loaded objects directly. I had to use select new for it to work:

return Ok(from u in db.Users
          where u.UserId == key
          select new User
          {
              UserId = u.UserId,
              Name = u.Name
          });

This did not work:

return Ok(from u in db.Users
          where u.UserId == key
          select u);

Answer 5

Set routePrefix to "api".

ODataConventionModelBuilder builder = new ODataConventionModelBuilder();
builder.EntitySet<CustomerType>("CustomerType");

config.MapODataServiceRoute(routeName: "ODataRoute", routePrefix: "api", model: builder.GetEdmModel());

Which OData version are you using? Check for correct namespaces, for OData V4 use System.Web.OData, for V3 System.Web.Http.OData. Namespaces used in controllers have to be consistent with the ones used in WebApiConfig.

Answer 6

Another thing to be taken into consideration is that the URL is case sensitive so:

localhost:xxx/api/Sites -> OK
localhost:xxx/api/sites -> HTTP 406