包括工作，但加入不工作 c# linq

Question

我正试图将所有汽车都交给车主。一位车主可以拥有多辆汽车，一辆汽车可以注册给一位车主。

如果我输入这样的查询，我会得到预期的结果：

public List<Owner> Get()
{
    var ownerWithCars = db.Owner.Include(o => o.Cars).AsNoTracking().ToList();
    return ownerWithCars;

}

但是这个查询不起作用：

public List<Owner> Get()
{
    var cars = from o in db.Owners join c in db.Cars on o.Id equals c.OwnerId into cars
               select new Owner() {Id = o.Id, Address = o.Address, Cars = cars.ToList()};
    return cars;
}

如果我运行第二个查询，我会收到以下错误：

"ExceptionMessage": "The 'ObjectContent`1' type failed to serialize the response body for content type 'application/json; charset=utf-8'.",

我已将以下内容添加到我的global.asax

        GlobalConfiguration.Configuration.Formatters.JsonFormatter.SerializerSettings
.ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore;
        GlobalConfiguration.Configuration.Formatters
            .Remove(GlobalConfiguration.Configuration.Formatters.XmlFormatter);

Answer 1

使用Include 第一个查询获得的结果集可以通过稍微不同地编写第二个查询来获得使用join。你可以试试：

public List<Owner> Get()
{
    var ownerWithCars = (from o in db.Owners
                join c in db.Cars on o.Id equals c.OwnerId into cars 
                select o).ToList();

    return ownerWithCars ;
}