asp.net – WebAPI Empty 500错误

这是数据类.

public class Comment
{
    public int Id { get; set; }
    public string Content { get; set; }
    public string Email { get; set; }
    public bool IsAnonymous { get; set; }

    public int ReviewId { get; set; }
    public Review Review { get; set; }
}
public class Review
{
    public int Id { get; set; }
    public string Content { get; set; }

    public int CategoryId { get; set; }
    public string Topic { get; set; }
    public string Email { get; set; }
    public bool IsAnonymous { get; set; }

    public virtual Category Category { get; set; }
    public virtual ICollection<Comment> Comments { get; set; }
}

这是来自ReviewRepository.cs的代码

public Review Get(int id)
{
    return _db.Reviews.Include("Comments").SingleOrDefault(r => r.Id == id);
}

以及来自ReviewController.cs的代码

public HttpResponseMessage Get(int id)
{
    var category = _reviewRepository.Get(id);
    if (category == null)
    {
        return Request.CreateResponse(HttpStatusCode.NotFound);
    }
    return Request.CreateResponse(HttpStatusCode.OK,category);
}

无论我做什么,从/ api / reviews / 1返回的响应都是500错误.调试时,类别是正确的,加载了所有注释.

我尝试了GlobalConfiguration.Configuration.IncludeErrorDetailPolicy = IncludeErrorDetailPolicy.Always;,但这没有帮助.我在这里不知所措！