entity-framework - 在 oData 控制器中加入 2 个实体后如何返回 IQueryable 结果

Question

我有两个表UU_DeliveryCharges和SC_Countries，我想在我的 odata 函数中将结果集作为这两个表的连接返回，但出现异常：

无法在 LINQ to Entities 查询中构造实体或复杂类型“ULYXModel.UU_DeliveryCharges”。

我是oData的新手，请帮忙。

oData Web API：

[EnableQuery] 
public IQueryable<UU_DeliveryCharges> GetUU_DeliveryCharges()
{
    //retrun db.UU_DeliveryCharges;

    var results = from deliveries in db.UU_DeliveryCharges                        
        join countries in db.SC_Countries on deliveries.CountryId equals countries.CountryId
        select new UU_DeliveryCharges
        {
            FlatRate = deliveries.FlatRate,
            MileRate = deliveries.MileRate,
            PickUpFee = deliveries.PickUpFee,
            DropOffFee = deliveries.DropOffFee,
            CountryName = countries.CountryName
        };

    return results;
}

模型：

public partial class UU_DeliveryCharges
{
    public int DeliveryChargeId { get; set; }     

    public Nullable<int> CountryId { get; set; }      

    public Nullable<decimal> MileRate { get; set; }

    public Nullable<decimal> FlatRate { get; set; }          

    public Nullable<decimal> PickUpFee { get; set; }

    public Nullable<decimal> DropOffFee { get; set; }           

    public string CountryName { get; set; }            
}  

public partial class SC_Countries
{
    public int CountryId { get; set; }

    public string CountryName { get; set; }           
}