vb.net intellisense not showing methods

Question

why does intellisense does not show some methods in vb.net?

e.g. HttpRequestMessageExtensions class from System.Net.Http is not shown at all.

this is ok with c#

public HttpResponseMessage GetProduct(int id)
{
    Product item = repository.Get(id);

    if (item == null)
    {
        var message = string.Format("Product with id = {0} not found", id);
        var err = new HttpError(message);
        err["error_sub_code"] = 42;
        return Request.CreateErrorResponse(HttpStatusCode.NotFound, err);
    }
    else
    {
         return Request.CreateResponse(HttpStatusCode.OK, item);
    }
}

Thanks

Kevin